Ring-opening Polymerization (ring-opening + polymerization)

Distribution by Scientific Domains

Kinds of Ring-opening Polymerization

  • anionic ring-opening polymerization
  • cationic ring-opening polymerization
  • controlled ring-opening polymerization

  • Selected Abstracts

    Ring-Opening Polymerization with Synergistic Co-monomers: Access to a Boronate-Functionalized Polymeric Monolith for the Specific Capture of cis -Diol-Containing Biomolecules under Neutral Conditions,

    ANGEWANDTE CHEMIE, Issue 36 2009
    Lianbing Ren
    Molekulare Teamarbeit: Synergistische Comonomere in einem Boronat-funktionalisierten Polymermonolithen wirken wie ein einzelner Boronsäureligand vom Wulff-Typ und ermöglichen die spezifische Bindung von cis -Diol-Biomolekülen unter neutralen Bedingungen (siehe Schema). Beim Ansäuern des Mediums wird die Aminogruppe protoniert und die B-N-Koordination aufgehoben, was zur Freisetzung des cis -Diols vom Monolithen führt. [source]

    Synthesis and rheology of biodegradable poly(glycolic acid) prepared by melt ring-opening polymerization of glycolide

    Estelle Gautier
    Abstract Ring-opening polymerization (ROP) of glycolide was studied in melt conditions and in the presence of two different initiators: 1-dodecanol and 1,4-butanediol and tin(II) 2-ethylhexanoate as catalyst. Its subsequent polymerization provided poly(glycolic acid) with controlled molar masses ranging from 2000 to 42,000 g/mol with well-defined structures characterized by NMR. Their thermal properties were evaluated by DSC analysis, and a glass transition temperature at infinite molar mass (Tg,) of 44.8 °C was thus calculated. From rheological data, the critical molar mass for entanglement, Mc, was estimated to be near 11,000 g/mol. Furthermore, in situ polymerizations were also performed between the plates of the rheometer within a same temperature range from 210 to 235 °C. The variation of the storage and loss moduli during the polymerization step have been monitored by time sweep oscillatory experiments under an angular frequency , = 10 rad/s. Finally, the development of an inverse rheological method allowed to calculate the bulk polymerization kinetics in the temperature range 200,230 °C. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 1440,1449, 2009 [source]

    Ring-opening polymerization of benzylated 1,6-anhydro-,- D -lactose and specific biological activities of sulfated (1,6)-,- D -lactopyranans

    Shuqin Han
    Abstract A new anhydro disaccharide monomer, 1,6-anhydro-2,3-di- o -benzyl-4- o -(2,,3,,4,,6,-tetra- o -benzyl-,- D -galactopyranosyl)-,- D -glucopyranose (benzylated 1,6-anhydro lactose (LSHBE)), was synthesized from D -lactose to investigate the polymerizability and biological activities of the resulting branched polysaccharides. The ring-opening polymerization of LSHBE was carried out with phosphorus pentafluoride as a catalyst under high vacuum to give a stereoregular benzylated (1 , 6)-,- D -lactopyranan. The molecular weights of poly(LSHBE)s increased with an increase in the amount of CH2Cl2 solvent, and polymerization temperatures were affected in both molecular weights and yields of the polymers. The copolymerization of LSHBE with benzylated 1,6-anhydro-,- D -glucopyranose (LGTBE) gave the corresponding copolysacchrides having different proportions of lactose and glucose units in good yields. After debenzylation to recover hydroxyl groups and then sulfation, sulfated homopoly(lactose)s and copoly(lactose and glucose)s were obtained. Sulfated homopoly(lactose)s had moderate anti-HIV (EC50 = 5.9 and 1.3 ,g/mL) and blood anticoagulant activities (AA = 18 and 13 unit/mg), respectively. Sulfated copoly(lactose and glucose) having 15 mol % lactose units gave high anti-HIV and blood anticoagulant activities of 0.3 ,g/mL and 54 unit/mg, respectively. These biological results suggest that the distance between branched units on the main chain plays an important role in the anti-HIV and blood anticoagulant activities. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 913,924, 2009 [source]

    Ring-opening polymerization of substituted ,-caprolactones with a chiral (salen) AlOiPr complex

    Mark R. Ten Breteler
    Abstract The ring-opening polymerization (ROP) of ,-caprolactone (,-CL), 4-methyl-,-caprolactone (4-MeCL), and 6-methyl-,-caprolactone (6-MeCL) with a single-site chiral initiator, R,R,-(salen) aluminum isopropoxide (R,R,-[1]), was investigated. The kinetic data for the ROP of the three monomers at 90° in toluene corresponded to first-order reactions in the monomer and propagation rate constants of k,-CL > k4-MeCL , k6-MeCL. A notable stereoselectivity with a preference for the R -enantiomer was observed in the ROP of 6-MeCL with R,R,-[1], whereas for 4-MeCL, no stereoselectivity was found. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 429,436, 2007. [source]

    Ring-opening polymerization and block copolymerization of L -lactide with divalent samarocene complex

    Dongmei Cui
    Abstract Divalent samarocene complex [(C5H9C5H4)2Sm(tetrahydrofuran)2] was prepared and characterized and used to catalyze the ring-opening polymerization of L -lactide (L-LA) and copolymerization of L-LA with caprolactone (CL). Several factors affecting monomer conversion and molecular weight of polymer, such as polymerization time, temperature, monomer/catalyst ratio, and solvent, were examined. The results indicated that polymerization was rapid, with monomer conversions reaching 100% within 1 h, and the conformation of L-LA was retained. The structure of the block copolymer of CL/L-LA was characterized by NMR and differential scanning calorimetry. The morphological changes during crystallization of poly(caprolactone) (PCL)- b -P(L-LA) copolymer were monitored with real-time hot-stage atomic force microscopy (AFM). The effect of temperature on the morphological change and crystallization behavior of PCL- b -P(L-LA) copolymer was demonstrated through AFM observation. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2667,2675, 2003 [source]

    Ring-opening polymerization of ,-caprolactone by a new yttrium complex: Y[2,2,-ethylidene-bis(4,6-di- tert -butylphenoxy)]2(ethylene glycol dimethyl ether)Na(ethylene glycol dimethyl ether)3

    Guangming Wu
    Abstract The main aims of the work reported here were to synthesize and characterize a new 2,2,-ethylidene-bis(4,6-di- tert -butylphenol) (EDBPH2)-based bimetal yttrium complex, Y(EDBP)2(DME)Na(DME)3 (1c; where DME is ethylene glycol dimethyl ether), which was employed as an efficient initiator for the ring-opening polymerization of ,-caprolactone (,-CL). From single-crystal X-ray diffraction, the solid structure of this new bimetal initiator was well established. Experimental results show that 1c initiates the ring-opening polymerization of ,-CL to afford poly(,-CL) with a narrow molecular weight distribution (Mw/Mn = 1.09,1.36, 65 °C). Based on an in situ NMR study, a plausible coordination,insertion mechanism is then proposed. The bimetal complex 1c can be used as an initiator for the ring-opening polymerization of ,-CL with some living characteristics. A study of the mechanism reveals that DME displacement in 1c by ,-CL is involved in the initiation process and the propagation may proceed through three pathways by NaO insertion or YO insertion. Copyright © 2009 Society of Chemical Industry [source]

    Ring-opening polymerization of D,L -lactide by rare earth 2,6-dimethylaryloxide

    Lifang Zhang
    Abstract Ring-opening polymerization of D,L -lactide (LA) has been successfully carried out by using rare earth 2,6-dimethylaryloxide (Ln(ODMP)3) as single component catalyst or initiator for the first time. The effects of different rare earth elements, solvents, monomers and catalyst concentration as well as polymerization temperature and time on the polymerization were investigated. The results show that La(ODMP)3 exhibits higher activity to prepare poly(D,L -lactide) (PLA) with a viscosity molecular weight of 4.5 × 104 g mol,1 and the conversion of 97 % at 100 °C in 45 min. The catalytic activity of Ln(ODMP)3 has following sequence: La > Nd > Sm > Gd > Er > Y. A kinetic study has indicated that the polymerization is first order with respect to both monomer and catalyst concentration. The apparent activation energy of the polymerization of LA with La(ODMP)3 is 69.6 kJ mol,1. The analyses of polymer ends indicate that the LA polymerization proceeds according to ,coordination,insertion' mechanism with selective cleavage of the acyl,oxygen bond of the monomer. Copyright © 2004 Society of Chemical Industry [source]

    Ring-opening polymerization of ,-caprolactone by lanthanide tris (2, 6-dimethylphenolate) s

    Li-Fang Zhang
    Abstract Lanthanide tris (2,6-dimethylphenolate)s [Ln(ODMP)3] were used as initiators for ring-opening polymerization of s -caprolactone (CL) for the first time. The influence of different rare earth elements and solvents was investigated. 1H NMR spectral data of polycaprolactone (PCL) obtained showed that the polymerization mechanism is in agreement with the coordination-insertion mechanism and the selective cleavage of the acyl-oxygen bond of CL. [source]

    Discrete, Base-Free, Cationic Alkaline-Earth Complexes , Access and Catalytic Activity in the Polymerization of Lactide

    Yann Sarazin
    Abstract Well-defined, base free cations of zinc and the alkaline-earth metals (Mg, Ca, Sr, Ba) supported by a multidentate phenolate ligand and stabilized by perfluorinated weakly coordinating counterions are readily available by simple procedures; the solid-state structures of the magnesium and calcium derivatives were elucidated. Upon treatment with an excess of iPrOH, these complexes generate highly efficient binary catalytic systems for the immortal ring-opening polymerization of L -lactide, yielding poly(L -lactide)s with controlled architectures and molecular features. [source]

    First Example of a Gold(I) N -Heterocyclic-Carbene-Based Initiator for the Bulk Ring-Opening Polymerization of L -Lactide

    Lipika Ray
    Abstract Synthesis, structure, and catalysis studies of two Au- and Ag-based initiators, namely, [3-(N - tert -butylacetamido)-1-(2-hydroxycyclohexyl)imidazol-2-ylidene]AuCl (1c) and [3-(N - tert -butylacetamido)-1-(2-hydroxycyclohexyl)imidazol-2-ylidene]AgCl (1b), for the bulk ring-opening polymerization of L -lactide are reported. Specifically, gold complex 1c was obtained from silver complex 1b by the transmetalation reaction with (SMe2)AuCl. Silver complex 1b was synthesized by the treatment of 3-(N - tert -butylacetamido)-1-(2-hydroxycyclohexyl)imidazolium chloride (1a) with Ag2O. Compound 1a was synthesized directly from the reaction of N - tert -butyl-2-chloroacetamide, cyclohexene oxide, and imidazole. The molecular structures of 1a, 1b, and 1c have been determined by X-ray diffraction studies. The formation of neutral monomeric complexes with linear geometries at the metal centers was observed for both 1b and 1c. The Au and Ag complexes 1c and 1b successfully catalyzed the bulk ring-opening polymerization of L -lactide at elevated temperatures under solvent-free melt conditions to produce moderate to low molecular weight polylactide polymers with narrow molecular weight distributions. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source]

    Photochromic Polymers Based on the Photoinduced Opening and Thermal Closing of [1,3]Oxazine Rings

    Massimiliano Tomasulo
    Abstract Two macromolecular constructs incorporating a single polymer backbone with multiple photochromic side chains are developed. Both systems are prepared from preformed photochromic [1,3]oxazines after the ring-opening polymerization of their norbornene appendages. In solution, UV illumination of these polymers opens the [1,3]oxazine rings in their side chains in less than 6,ns and with a quantum yield of 0.09 in both instances. The photogenerated species incorporate a 4-nitrophenolate chromophore, and hence, their formation is accompanied by the appearance of an intense band in the visible region of the absorption spectrum. The photoproducts revert spontaneously to the original state with first-order kinetics in microseconds. Furthermore, both photochromic polymers tolerate hundreds of switching cycles with no sign of degradation, even in the presence of molecular oxygen. Thus, this design logic and choice of functional building blocks can translate into the realization of innovative photoresponsive materials with excellent photochromic performance. [source]

    Synthesis,Structure,Property Relationships for Hyperbranched Aminosilica CO2 Adsorbents

    Jeffrey H. Drese
    Abstract Hyperbranched aminosilica (HAS) adsorbents are prepared via the ring-opening polymerization of aziridine in the presence of mesoporous silica SBA-15 support. The aminopolymers are covalently bound to the silica support and capture CO2 reversibly in a temperature swing process. Here, a range of HAS materials are prepared with different organic loadings. The effects of organic loading on the structural properties and CO2 adsorption properties of the resultant hybrid materials are examined. The residual porosity in the HAS adsorbents after organic loading, as well as the molecular weights and degrees of branching for the separated aminopolymers, are determined to draw a relationship between adsorbent structure and performance. Humid adsorption working capacities and apparent adsorption kinetics are determined from experiments in a packed-bed flow system monitored by mass spectrometry. Dry adsorption isotherms are presented for one HAS adsorbent with a high amine loading at 35 and 75,°C. These combined results establish the relationships between adsorbent synthesis, structure, and CO2 adsorption properties of the family of HAS materials. [source]

    pH-Responsive Flower-Type Micelles Formed by a Biotinylated Poly(2-vinylpyridine)- block -poly(ethylene oxide)- block -poly(, -caprolactone) Triblock Copolymer

    Kathy Van Butsele
    Abstract In the present work, a method is proposed to assemble pH-responsive, flower-like micelles that can expose a targeting unit at their periphery upon a decrease in pH. The micelles are composed of a novel biotinylated triblock copolymer of poly(,, -caprolactone)- block -poly(ethylene oxide)- block -poly(2-vinylpyridine) (PCL- b -PEO- b -P2VP) and the non-biotinylated analogue. The block copolymers are synthesized by sequential anionic and ring-opening polymerization. The pH-dependent micellization behaviour in aqueous solution of the triblock copolymers developed is studied using dynamic light scattering, zeta potential, transmission electron microscopy (TEM), and fluorimetric measurements. The shielding of the biotin at neutral pH and their availability at the micelle surface upon protonation is established by TEM and surface plasmon resonance with avidin and streptavidin-coated gold surfaces. The preliminary stealthy behavior of these pH-responsive micelles is examined using the complement activation (CH50) test. [source]

    Poly(,-caprolactone)-Functionalized Carbon Nanotubes and Their Biodegradation Properties,

    H.-L. Zeng
    Abstract Biodegradable poly(,-caprolactone) (PCL) has been covalently grafted onto the surfaces of multiwalled carbon nanotubes (MWNTs) by the "grafting from" approach based on in-situ ring-opening polymerization of ,-caprolactone. The grafted PCL content can be controlled easily by adjusting the feed ratio of monomer to MWNT-supported macroinitiators (MWNT-OH). The resulting products have been characterized with Fourier-transform IR (FTIR), NMR, and Raman spectroscopies, transmission electron microscopy (TEM), and scanning electron microscopy (SEM). After PCL was coated onto MWNT surfaces, core/shell structures with nanotubes as the "hard" core and the hairy polymer layer as the "soft" shell are formed, especially for MWNTs coated with a high density of polymer chains. Such a polymer shell promises good solubility/dispersibility of the MWNT,PCL nanohybrids in low-boiling-point organic solvents such as chloroform and tetrahydrofuran. Biodegradation experiments have shown that the PCL grafted onto MWNTs can be completely enzymatically degraded within 4,days in a phosphate buffer solution in the presence of pseudomonas (PS) lipase, and the carbon nanotubes retain their tubelike morphologies, as observed by SEM and TEM. The results present possible applications for these biocompatible PCL-functionalized CNTs in bionanomaterials, biomedicine, and artificial bones. [source]

    Anionic ring-opening polymerization of small phosphorus heterocycles and their borane adducts: An ab initio investigation

    Michelle L. Coote
    The kinetics and thermodynamics of anionic ring-opening reactions of phosphiranes, phosphetanes, and phospholanes and their borane adducts have been studied by high-level ab initio procedures. For the free heterocycles, model propagation reactions involving nucleophilic attack by Me2P, at the ring ,-carbon were found to be feasible for the three- and four-membered rings, but not for the five-membered ring. For the borane adducts, nucleophilic attack by Me2(BH3)P, was only facile for the three-membered ring, despite an increased thermodynamic tendency toward ring opening for the borane adducts of both the three- and four-membered rings. The formation constants of the borane adducts of methylphosphirane and methylphosphetane were K = 2.6 × 1013 L mol,1 and K = 1.2 × 1020 L mol,1, respectively. A Marcus analysis of the ring-opening reactions of methylphosphirane, methylphosphetane, and their borane adducts showed that the release of ring strain and an "additional factor" contribute to rate enhancement compared with their strain-free analogues. The additional factor was larger for the three-membered rings than for the four-membered rings and was larger in the free heterocycles than in their borane adducts. The additional factor is complex in origin and appears to reflect an increase in the separation between the bonding and antibonding orbitals of the breaking bond on going from the three-membered rings to the four-membered rings, and on going from the free heterocycles to the borane adducts. © 2007 Wiley Periodicals, Inc. Heteroatom Chem 18:118,128, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20323 [source]

    Poly(trimethylene carbonate) from Biometals-Based Initiators/Catalysts: Highly Efficient Immortal Ring-Opening Polymerization Processes

    Marion Helou
    Abstract The ring-opening polymerization (ROP) of trimethylene carbonate (TMC) was evaluated in bulk at 60,110,°C using various catalyst systems based on bio-friendly metals, including the metal bis(trimethylsilylamides) Mg[N(SiMe3)2]2, Ca[N(SiMe3)2]2(THF)2, Y[N(SiMe3)2]3, (BDI)Fe[N(SiMe3)2] [BDI=CH(CMeNC6H3 -2,6- i- Pr2)2], Fe[N(SiMe3)2]2, Fe[N(SiMe3)2]3, Zn[N(SiMe3)2]2, (BDI)Zn[N(SiMe3)2] and ZnEt2, associated with an alcohol such as isopropyl or benzyl alcohol. The actual metal alkoxide initiating species has been formed in situ prior to the addition of TMC. Introduction of the alcohol component in excess leads to the "immortal" ring-opening polymerization (ROP) of TMC. According to such an "immortal" ROP process of TMC, whichever the metal species, as many as 200 polycarbonate chains could be successfully grown from a unique metal center in a well controlled ROP process. The best performances were obtained using the discrete (BDI)Zn[N(SiMe3)2] precursor. Under optimized conditions, as many as 50,000 equivalents of TMC could be fully converted from as little as 20,ppm of this metallic precursor, allowing the preparation of a polytrimethylene carbonate (PTMC) with a molar mass as high as 185,200,g,mol,1 with a relatively narrow molar mass distribution (Mw/Mn=1.68). A double monomer feed experiment carried out with the (BDI)Zn[N(SiMe3)2]/BnOH initiating system proved the "living" character of the polymerization. Characterization of the PTMCs by NMR and size exclusion chromatography (SEC) showed well-defined ,-hydroxy-,-alkoxycarbonate telechelic polymers, highlighting the controlled character of this "living and immortal" ROP process. Using the (BDI)Zn[N(SiMe3)2] precursor, varying the alcohol (ROH) to 2-butanol, 3-buten-2-ol or 4-(trifluoromethyl)benzyl alcohol, revealed the versatility of this approach, allowing the preparation of accordingly end-functionalized HO-PTMC-OR polymers. The very low initial loading of metal catalyst considerably limits the potential toxicity and thus allows such polycarbonates to be used in the biomedical field. [source]

    Synthesis and properties of poly(butylene terephthalate)/multiwalled carbon nanotube nanocomposites prepared by in situ polymerization and in situ compatibilization

    Fangjuan Wu
    Abstract A novel cyclic initiator was synthesized from dibutyl tin(IV) oxide and hydroxyl-functionalized multiwalled carbon nanotubes (MWNTs) and was used to initiate the ring-opening polymerization of cyclic butylene terephthalate oligomers to prepare poly(butylene terephthalate) (PBT)/MWNT nanocomposites. The results of Fourier transform infrared and NMR spectroscopy confirmed that a graft structure of PBT on the MWNTs was formed during the in situ polymerization; this structure acted as an in situ compatibilizer in the nanocomposites. The PBT covalently attached to the MWNT surface enhanced the interface adhesion between the MWNTs and PBT matrix and, thus, improved the compatibility. The morphologies of the nanocomposites were observed by field emission scanning electron microscopy and transmission electron microscopy, which showed that the nanotubes were homogeneously dispersed in the PBT matrix when the MWNT content was lower than 0.75 wt %. Differential scanning calorimetry and thermogravimetric analysis were used to investigate the thermal properties of the nanocomposites. The results indicate that the MWNTs acted as nucleation sites in the matrix, and the efficiency of nucleation was closely related to the dispersion of the MWNTs in the matrix. Additionally, the thermal stability of PBT was improved by the addition of the MWNTs. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source]

    Synthesis and characterization of a cured epoxy resin with a benzoxazine monomer containing allyl groups

    Shiao-Wei Kuo
    Abstract Vinyl-terminated benzoxazine (VB-a), which can be polymerized through ring-opening polymerization, was synthesized through the Mannich condensation of bisphenol A, formaldehyde, and allylamine. This VB-a monomer was then blended with epoxy resin and then concurrently thermally cured to form an epoxy/VB-a copolymer network. To understand the curing kinetics of this epoxy/VB-a copolymer, dynamic differential scanning calorimetry measurements were performed by the Kissinger and Flynn,Wall,Ozawa methods. Fourier transform infrared (FTIR) analyses revealed the presence of thermal curing reactions and hydrogen-bonding interactions of the epoxy/VB-a copolymers. Meanwhile, a significant enhancement of the ring-opening and allyl polymerizations of the epoxy was observed. For these interpenetrating polymer networks, dynamic mechanical analysis and thermogravimetric analysis results indicate that the thermal properties increased with increasing VB-a content in the epoxy/VB-a copolymers. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source]

    Evaluation of polymethacrylic ionomer as compatibilizers for MCPA6/clay composites

    Tongfei Wu
    Abstract The compatibilization effects provided by polymethacrylic ionomer (PMMA ionomer) on monomer-casting polyamide6 (MCPA6)/clay (pristine sodium montmorillonite) composites were studied in this work. The PMMA ionomer used in this study was sodium polymethacrylate ionomer (PMMA Na+ -ionomer), which is a copolymer of methyl methacrylate and sodium methacrylate, prepared using emulsion polymerization. MCPA6/clay/PMMA Na+ -ionomer composites were prepared by in situ anionic ring-opening polymerization (AROP) of ,-caprolactam (CLA). X-ray diffraction (XRD) and transmission electron microscopy (TEM) plus rheological measurement were used to characterize those composites. The results indicated that PMMA Na+ -ionomer is a good compatibilizer for this system. With increasing PMMA Na+ -ionomer content, a better dispersion of clay layers was successfully achieved in the MCPA6 matrix. Furthermore, differential scanning calorimetry (DSC) and XRD results indicated that well dispersed silicate layers limit the mobility of the MCPA6 molecule chains to crystallize, reduce the degree crystalline, and favor the formation of the ,-crystalline form of the MCPA6 matrix. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source]

    Surface modification of starch nanocrystals through ring-opening polymerization of ,-caprolactone and investigation of their microstructures

    Hassan Namazi
    Abstract Bionanoparticles of starch obtained by submitting native potato starch granules to acid hydrolysis conditions. The resulted starch nanoparticles were used as core or macro initiator for polymerization of ,-caprolactone (CL). Starch nanoparticle- g -polycaprolactone was synthesized through ring-opening polymerization (ROP) of CL in the presence of Sn(Oct)2 as initiator. The detailed microstructure of the resulted copolymer was characterized with NMR spectroscopy. Thermal characteristic of the copolymer was investigated using DSC and TGA. By introducing PCL, the range of melting temperature for starch was increased and degradation of copolymer occurred in a broader region. X-ray diffraction and TEM micrographs confirmed that there was no alteration of starch crystalline structure and morphology of nanoparticles, respectively. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source]

    Comparative study of the hydrolytic degradation of glycolide/L -lactide/,-caprolactone terpolymers initiated by zirconium(IV) acetylacetonate or stannous octoate

    Janusz Kasperczyk
    Abstract A series of copolymers have been synthesized by the ring-opening polymerization of glycolide, L -lactide, and ,-caprolactone with zirconium(IV) acetylacetonate [Zr(Acac)4] or stannous octoate [Sn(Oct)2] as the catalyst. The resulting terpolymers have been characterized by analytical techniques such as proton nuclear magnetic resonance, size exclusion chromatography, and differential scanning calorimetry. Data have confirmed that Sn(Oct)2 leads to less transesterification of polymer chains than Zr(Acac)4 under similar conditions. The various copolymers have been compression-molded and allowed to degrade in a pH 7.4 phosphate buffer at 37°C. The results show that the degradation rate depends not only on the copolymer composition but also on the chain microstructure, the Sn(Oct)2 -initiated copolymers degrading less rapidly than Zr(Acac)4 -initiated ones with more random chain structures. The caproyl component appears the most resistant to degradation as its content increases in almost all cases. Moreover, caproyl units exhibit a protecting effect on neighboring lactyl or glycolyl units. The glycolyl content exhibits different features: it decreases because of faster degradation of glycolyl units, which are more hydrophilic than caproyl and lactyl ones, remains stable in the case of abundant CGC sequences, which are very resistant to degradation, or even increases because of the formation of polyglycolide crystallites. Terpolymers can crystallize during degradation if the block length of one of the components is sufficiently long, even though they are amorphous initially. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source]

    A positive-working photosensitive polyimide based on thermal cross-linking and acidolytic cleavage

    Myung-Sup Jung
    Abstract A novel positive-working photosensitive polyimide (PSPI) based on a poly(hydroxyimide) (PHI), a crosslinking agent having vinyl ether groups, and a photoacid generator (PAG) was prepared. The PHI as a base resin of the three-component PSPI was synthesized from 4,4,-oxydiphthalic anhydride and 2,2,-bis(3-amino-4-hydroxyphenyl)hexafluoropropane through ring-opening polymerization and subsequent thermal cyclization. 2,2,-bis(4-(2-(vinyloxy)ethoxy)phenyl)propane (BPA-DEVE) was used as a vinylether compound and diphenyliodonium 5-hydroxynaphthalene-1-sulfonate was used as a PAG. The phenolic hydroxyl groups of the PHI and the vinyl ether groups of BPA-DEVE are thermally crosslinked with acetal structures during prebake step, and the crosslinked PHI becomes completely insoluble in an aqueous basic solution. Upon exposure to UV light (365 nm) and subsequent postexposure bake (PEB), a strong acid generated from the PAG cleaves the crosslinked structures, and the exposed area is effectively solubilized in the alkaline developer. The dissolution behavior of the PSPI containing each 11.5 wt % of BPA-DEVE and of the PAG was studied after UV exposure (365 nm) and PEB. It was found that the difference in dissolution rates between exposed and unexposed areas was enough to get high resolution. A fine positive pattern with a resolution of 5 ,m in a 3.7-,m-thick film was obtained from the three-component PSPI. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source]

    Modification of carbon black through grafting multihydroxyl hyperbranched polyether onto its surface

    Qiang Yang
    Abstract The hydroxy methyl groups were introduced onto the pristine carbon black surface through the reaction between unsaturated hydrogen atoms of the polycondensed aromatic rings of carbon black and formaldehyde in alkali condition. Using the resultant hydroxy methyl groups on the carbon black surface as the growth point, multihydroxyl hyperbranched polyether was grafted onto the carbon black surface by cationic ring-opening polymerization of 3-ethyl-3-(hydroxymethyl)-oxetane in the presence of BF3·OEt2 to improve its dispersion ability in solvents. It was found that the modified carbon black could be dispersed in polar solvents, such as ethanol, chloroform, and DMF. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2086,2092, 2007 [source]

    Synthesis and self-assembly of well-defined cyclodextrin-centered amphiphilic A14B7 multimiktoarm star copolymers based on poly(,-caprolactone) and poly(acrylic acid)

    Peng-Fei Gou
    Abstract Novel amphiphilic A14B7 multimiktoarm star copolymers composed of 14 poly(,-caprolactone) (PCL) arms and 7 poly(acrylic acid) (PAA) arms with ,-cyclodextrin (,-CD) as core moiety were synthesized by the combination of controlled ring-opening polymerization (CROP) and atom transfer radical polymerization (ATRP). 14-Arm star PCL homopolymers (CDSi-SPCL) were first synthesized by the CROP of CL using per-6-(tert -butyldimethylsilyl)-,-CD as the multifunctional initiator in the presence of Sn(Oct)2 at 125 °C. Subsequently, the hydroxyl end groups of CDSi-SPCL were blocked by acetyl chloride. After desilylation of the tert -butyldimethylsilyl ether groups from the ,-CD core, 7 ATRP initiating sites were introduced by treating with 2-bromoisobutyryl bromide, which further initiated ATRP of tert -butyl acrylate (tBA) to prepare well-defined A14B7 multimiktoarm star copolymers [CDS(PCL-PtBA)]. Their molecular structures and physical properties were in detail characterized by 1H NMR, SEC-MALLS, and DSC. The selective hydrolysis of tert -butyl ester groups of the PtBA block gave the amphiphilic A14B7 multimiktoarm star copolymers [CDS(PCL-PAA)]. These amphiphilic copolymers could self-assemble into multimorphological aggregates in aqueous solution, which were characterized by dynamic light scattering (DLS), transmission electron microscopy (TEM) and atomic force microscopy (AFM). © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2961,2974, 2010 [source]

    Thermoresponsive brush copolymers with poly(propylene oxide- ran -ethylene oxide) side chains via metal-free anionic polymerization "grafting from" technique

    Junpeng Zhao
    Abstract Thermoresponsive brush copolymers with poly(propylene oxide- ran -ethylene oxide) side chains were synthesized via a "grafting from" technique. Poly(p -hydroxystyrene) was used as the backbone, and the brush copolymers were prepared by random copolymerization of mixtures of oxyalkylene monomers, using metal-free anionic ring-opening polymerization, with the phosphazene base (t -BuP4) being the polymerization promoter. By controlling the monomer feed ratios in the graft copolymerization, two samples with the same side-chain length and different compositions were prepared, both of which possessed high molecular weights and low molecular weight distributions. The results from light scattering and fluorescence spectroscopy indicated that the brush copolymers in their dilute aqueous solutions were near completely solvated at low temperature and underwent slight intramolecular chain contraction/association and much more profound intermolecular aggregation at different stages of the step-by-step heating process. Above 50 °C, very turbid solutions, followed by macrophase separation, were observed for both of the samples, which implied that it was difficult for the brush copolymers to form stable nanoscopic aggregates at high temperature. All these observations were attributed, at least partly, to the distribution of the oxyalkylene monomers along the side chains and the overall brush-like molecular architecture. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2320,2328, 2010 [source]

    Chemistry of 2-oxazolines: A crossing of cationic ring-opening polymerization and enzymatic ring-opening polyaddition

    Akira Makino
    Abstract Chemistry of 2-oxazolines is involved in the polymer synthesis fields of cationic ring-opening polymerization (CROP) and enzymatic ring-opening polyaddition (EROPA), although both polymerizations look like a quite different class of reaction. The key for the polymerization to proceed is combination of the catalyst (initiator) and the design of monomers. This article describes recent developments in polymer synthesis via these two kinds of polymerizations to afford various functional polymers having completely different structures, poly(N -acylethylenimine)s via CROP and 2-amino-2-deoxy sugar unit-containing oligo and polysaccharides via EROPA, respectively. From the viewpoint of reaction mode, an acid-catalyzed ring-opening polyaddition (ROPA) is considered to be a crossing where CROP and EROPA meet. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1251,1270, 2010 [source]

    Titanium-mediated [CpTiCl2(OEt)] ring-opening polymerization of lactides: A novel route to well-defined polylactide-based complex macromolecular architectures

    Nikolaos Petzetakis
    Abstract Among three cyclopentadienyl titanium complexes studied, CpTiCl2(OEt), containing a 5% excess CpTiCl3, has proven to be a very efficient catalyst for the ring-opening polymerization (ROP) of L -lactide (LLA) in toluene at 130 °C. Kinetic studies revealed that the polymerization yield (up to 100%) and the molecular weight increase linearly with time, leading to well-defined PLLA with narrow molecular weight distributions (Mw/Mn , 1.1). Based on the above results, PS- b -PLLA, PI- b -PLLA, PEO- b -PLLA block copolymers, and a PS- b -PI- b -PLLA triblock terpolymer were synthesized. The synthetic strategy involved: (a) the preparation of OH-end-functionalized homopolymers or diblock copolymers by anionic polymerization, (b) the reaction of the OH-functionalized polymers with CpTiCl3 to give the corresponding Ti-macrocatalyst, and (c) the ROP of LLA to afford the final block copolymers. PMMA- g -PLLA [PMMA: poly(methyl methacrylate)] was also synthesized by: (a) the reaction of CpTiCl3 with 2-hydroxy ethyl methacrylate, HEMA, to give the Ti-HEMA-catalyst, (b) the ROP of LLA to afford a PLLA methacrylic-macromonomer, and (c) the copolymerization (conventional and ATRP) of the macromonomer with MMA to afford the final graft copolymer. Intermediate and final products were characterized by NMR spectroscopy and size exclusion chromatography, equipped with refractive index and two-angle laser light scattering detectors. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1092,1103, 2010 [source]

    Organic,inorganic hybrid brushes consisting of macrocyclic oligomeric silsesquioxane and poly(,-caprolactone): Synthesis, characterization, and supramolecular inclusion complexation with ,-cyclodextrin

    Jin Han
    Abstract Organic,inorganic hybrid brushes comprised of macrocyclic oligomeric silsesquioxane (MOSS) and poly(,-caprolactone) (PCL) were synthesized via the ring-opening polymerization of ,-caprolactone (CL) with cis- hexa[(phenyl) (2-hydroxyethylthioethyldimethylsiloxy)]cyclohexasiloxane as the initiator. The MOSS macromer bearing hydroxyl groups was synthesized via the thiol-ene radical addition reaction between cis -hexa[(phenyl)(vinyldimethylsiloxy)]cyclohexasiloxane and ,-mercaptoethanol. The organic,inorganic PCL cyclic brushes were characterized by means of nuclear magnetic resonance spectroscopy (NMR) and gel permeation chromatography (GPC). These MOSS,PCL brushes were then used to prepare the supramolecular inclusion complexes with ,-cyclodextrin (,-CD). The X-ray diffraction (XRD) indicates that the organic,inorganic inclusion complexes (ICs) have a channel-type crystalline structure. It is noted that the molar ratios of CL unit to ,-CD for the organic,inorganic ICs are quite dependent on the lengths of the PCL chains bonded to the silsesquioxane macrocycle. While the PCL chains were short, the efficiency of inclusion complexation was significantly decreased. The decreased efficiency could be attributed to the repulsion of the adjacent PCL chains bonded to the silsesquioxane macrocycle and the restriction of the bulky silsesquioxane macrocycle on the motion of PCL chains; this effect is pronounced with decreasing the length of the PCL chains. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2009 [source]

    Preparation of three-dimensional poly(dimethylsiloxane) (PDMS) with movable cross-linking

    Kazuya Miki
    Abstract A pentamethylcyclotrisiloxane moiety was introduced into cyclic polystyrene (cPSt) and cyclic PDMS (cPDMS) to obtain noncovalent cross-linking agents, D3 - cPSt and D3 - cPDMS, respectively. Anionic ring-opening polymerization of octamethylcyclotetrasiloxane (D4) in nitrobenzene was carried out in the presence of D3 - cPSt to obtain a cloudy white PDMS gel as a precipitation. On the other hand, bulk copolymerization of D3 - cPDMS with D4 proceeded in a homogeneous state to give a colorless transparent PDMS gel in high yield. The formation of mechanically linked PDMS with movable cross-linking was indicated by control experiment. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5882,5890, 2009 [source]

    An efficient approach to synthesize polysaccharides- graft -poly(p -dioxanone) copolymers as potential drug carriers

    Fang Lu
    Abstract Starch and poly(p -dioxanone) (PPDO) are the natural and synthetic biodegradable and biocompatible polymers, respectively. Their copolymers can find extensive applications in biomedical materials. However, it is very difficult to synthesize starch- graft -PPDO copolymers in common organic solvents with very good solubility. In this article, well-defined polysaccharides- graft -poly(p -dioxanone) (SAn -PPDO) copolymers were successfully synthesized via the ring-opening polymerization of p -dioxanone (PDO) with an acetylated starch (SA) initiator and a Sn(Oct)2 catalyst in bulk. The copolymers were characterized via Fourier transform infrared spectroscopy, 1H NMR, gel permeation chromatography, thermogravimetric analysis (TG), differential scanning calorimetry, and wide angle x-ray diffraction. The in vitro degradation results showed that the introduction of SA segments into the backbone chains of the copolymers led to an enhancement of the degradation rate, and the degradation rate of SAn -PPDO increased with the increase of SA wt %. Microspheres with an average volume diameter of 20 ,m, which will have potential applications in controlled release of drugs, were successfully prepared by using these new copolymers. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5344,5353, 2009 [source]