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Multifunctional Initiator (multifunctional + initiator)
Selected AbstractsSynthesis and self-assembly of well-defined cyclodextrin-centered amphiphilic A14B7 multimiktoarm star copolymers based on poly(,-caprolactone) and poly(acrylic acid)JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 14 2010Peng-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] Copolymerization of poly(vinyl alcohol)- graft -poly(1,4-dioxan-2-one) with designed molecular structure by a solid-state polymerization methodJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 9 2006Si-Chong Chen Abstract Poly(vinyl alcohol)- graft -poly(1,4-dioxan-2-one) (PVA- g -PPDO) with designed molecular structure was synthesized by a solid-state polymerization. The solid-state copolymerization was preceded by a graft copolymerization of PDO initiated with PVA as a multifunctional initiator, and Sn (Oct)2 as a coininitiator/catalyst in a homogeneous molten state. The polymerization temperature was then decreased and the copolymerization was carried out in a solid state. The products prepared by solid-state polymerization were characterized by 1H NMR and DSC, and were compared with those synthesized in the homogeneous molten state. The degree of polymerization (Dp), degree of substitution (Ds), yield and the average molecular weight of the graft copolymer with different molecular structure were calculated from the 1H NMR spectra. The results show that the crystallization process during the solid-state polymerization may suppress the undesirable inter- or intramolecular side reactions, then resulting in a controlled molecular structure of PVA- g -PPDO. The results of DSC measurement show that the molecular structures determine the thermal behavior of the PVA- g -PPDO. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3083,3091, 2006 [source] Accelerated iterative strategy for the divergent synthesis of dendritic macromolecules using a combination of living radical polymerization and an irreversible terminator multifunctional initiatorJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 20 2005Virgil Percec Abstract Our laboratory has reported the elaboration of an iterative strategy for the synthesis of dendritic macromolecules from conventional monomers. This synthetic method involves a combination of self-regulated metal-catalyzed living radical polymerization initiated from arenesulfonyl chlorides and an irreversible terminator multifunctional initiator (TERMINI). The previous TERMINI, (1,1-dimethylethyl)[[1-[3,5-bis(S -phenyl-4- N,N, diethylthiocarbamate)phenyl]ethenyl]oxy]dimethylsilane, was prepared in nine reaction steps. The replacement of the previous TERMINI with one that requires only three steps for its synthesis, diethylthiocarbamic acid S -{3-[1-(tert -butyl-dimethyl-silanyloxy)-vinyl]-5-diethylcarbamoylsulfanyl-phenyl} ester, and the use of the more reactive Cu2S/2,2,-bipyridine rather than the Cu2O/2,2,-bipyridine self-regulated catalyst have generated an accelerated method for the synthesis of dendritic macromolecules. This method provides rational design strategies for the synthesis of dendritic macromolecules with different compaction by the use of a single monomer. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4894,4906, 2005 [source] Rapid Synthesis and MALDI-ToF Characterization of Poly(ethylene oxide) Multiarm Star PolymersMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 1 2010Maria Doycheva Abstract Multiarm PEO star polymers with a purely aliphatic polyether structure have been synthesized using hyperbranched polyglycerol (PG) with different molecular weights as a multifunctional initiator. Different degrees of deprotonation of the initiator were studied with respect to molecular weight control. The results show that the degree of deprotonation is a crucial parameter for the synthesis of well-defined polymers with controlled molecular weights. Partial deprotonation of the PG hydroxyl groups (5,8%) was proven to represent an optimum for the synthesis of star polymers with molecular masses close to the theoretical values. Molecular weights of the stars ranged between 9,000 and 30,000,g,·,mol,1. MALDI-ToF spectra confirmed that the PEO arms in the star polymers possess homogeneous lengths. [source] Synthesis and characterization of optically active star-shaped poly (N -phenylmaleimide)s with a calixarene corePOLYMER INTERNATIONAL, Issue 6 2007Liping Lou Abstract Two N -phenylmaleimide derivatives bearing a chiral oxazoline group, N -[o -(4-phenyl-4,5-dihydro-1,3-oxazol-2-yl)phenyl]maleimide [(R)-PhOPMI] and N -[o -(4-isopropyl-4,5-dihydro-1,3-oxazol-2-yl)phenyl]maleimide [(S)-PriOPMI], were polymerized using in situ generated calixarene-based phenates as initiators to yield optically active polymers. The formation of star-shaped architectures was strongly dependent on both polymerization conditions and calixarene moieties. In the case of polymerization conducted in toluene at 80,100 °C, the arm-chain numbers achieved their respective maxima for the polymers with these multifunctional initiators. In contrast, the polymers obtained in polymerizations at lower temperature possessed fewer arm chains. The structure and chiroptical properties were investigated on the basis of 13C NMR, multiangular laser light scattering, gel permeation chromatography, and circular dichroism for the macromolecules with calixarene cores. Copyright © 2006 Society of Chemical Industry [source] | ||||||||||