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Macromolecular Architectures (macromolecular + architecture)

Distribution by Scientific Domains
Polymers and Materials Science87%

Kinds of Macromolecular Architectures

  • complex macromolecular architecture
    		•

    Selected Abstracts

    Functional syndiotactic poly(,-hydroxyalkanoate)s via stereoselective ring-opening copolymerization of rac -,-butyrolactone and rac -allyl-,-butyrolactone

    JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 12 2009
    Noureddine Ajellal
    Abstract The copolymerization of racemic ,-butyrolactone (rac -BLMe) with racemic "allyl-,-butyrolactone" (rac -BLallyl) in toluene, catalyzed by the discrete amino-alkoxy-bis(phenolate) yttrium-amido complex 1, gave new poly(,-hydroxyalkanoate)s with unsaturated side chains. The poly(BLMe - co -BLallyl) copolymers produced have a highly syndiotactic backbone structure (Pr = 0.80,0.84) with a random enchainment of monomer units, as evidenced by 13C NMR, and high molecular weight (Mn up to 58,000 g mol,1) with a narrow polydispersity (Mw/Mn = 1.07,1.37), as determined by GPC. The comonomer incorporation (5,50 mol % rac -BLallyl) was a linear function of the feed ratio. The pendant vinyl bond of the side-chains in those poly(BLMe - co -BLallyl) copolymers allowed the effective introduction of hydroxy or epoxy groups via dihydroxylation, hydroboration-oxidation or epoxidation reactions. NMR studies indicated that all of these transformations proceed in an essentially quantitative conversion and do not affect the macromolecular architecture. Some thermal properties (Tm, ,Hm, Tg) of the prepared polymers have been also evaluated. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3177,3189, 2009 [source]

    Synthesis, Characterization, and Folding Behavior of ,-Amino Acid Derived Polyisocyanides

    CHEMISTRY - A EUROPEAN JOURNAL, Issue 10 2006
    Sander J. Wezenberg
    Abstract Helical polymers of isocyanopeptides derived from ,-amino acids have been synthesized and their architectures have been studied in detail. Similar to their ,-amino acid analogues, the helical conformation in these macromolecules is stabilized by internal hydrogen-bonding arrays along the polymeric backbone. Unexpectedly, the flexibility of the ,-peptide side arms results in a rearrangement of the initial macromolecular architecture, leading to a more stable helical structure possessing a better defined hydrogen-bonding pattern, as was concluded from IR and temperature-dependent circular dichroism studies. Based on these results we propose a dynamic helical model for the ,-amino acid derived polyisocyanopeptides; this model is in contrast to the kinetically stable helical macromolecules that are formed upon polymerization of ,-amino acid based isocyanopeptides. [source]

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

    JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 5 2010
    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]

    Well-defined complex macromolecular architectures by anionic polymerization of styrenic single and double homo/miktoarm star-tailed macromonomers

    JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 5 2008
    Paraskevi Driva
    Abstract Styrenic single and double star-tailed macromonomers were synthesized by selective reaction of living homo/miktoarm stars with the chlorosilane groups of 4-(chlorodimethylsilyl)- and 4-(dichloromethylsilyl)styrene, respectively. The in situ anionic homopolymerization of macromonomers with sec -BuLi and copolymerization with butadiene and styrene, led to single/double homo/miktoarm star-tailed molecular brushes and combs, as well as a block copolymer consisting of a linear polystyrene chain and a double miktoarm (PBd/PS) star-tailed brush-like block. Molecular characterization by size exclusion chromatography, size exclusion chromatography/two-angle laser light scattering, and NMR spectroscopy, revealed the high molecular/compositional homogeneity of all intermediate and final products. These are only a few examples of the plethora of complex architectures possible using the above macromonomers. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 1826,1842, 2008 [source]

    Recent advances in the synthesis of well-defined glycopolymers

    JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 11 2007
    Sebastian G. Spain
    Abstract Glycopolymers are receiving increasing interest due to their application in areas, such as glycomics, medicine, biotechnology, sensors, and separation science. Consequently, new methods for their synthesis are constantly being developed, with an increasing emphasis on the preparation of well-defined polymers and on the production of complex macromolecular architectures such as stars. This review covers recent developments in the synthesis of glycopolymers, with a particular emphasis on (i) the use of controlled radical polymerization to prepare well-defined glycopolymers from unprotected monomers and (ii) postpolymerization modification strategies using reactive polymer precursors (including "click" reactions). Recent work on the production of glycosylated polypeptides, which are under investigation as mimics of naturally occurring glycoproteins, is also included. The authors offer some suggestions as to future developments and remaining challenges in this topical area of polymer chemistry. © 2007 Wiley Periodicals, Inc. J Polym Sci PartA: Polym Chem45: 2059,2072, 2007 [source]

    Metal,Ligand-Containing Polymers: Terpyridine as the Supramolecular Unit

    MACROMOLECULAR RAPID COMMUNICATIONS, Issue 9-10 2010
    Raja Shunmugam
    Abstract New and interesting properties can be obtained from macromolecular architectures functionalized with supramolecular moieties, particularly metal,ligand complexes. Self-assembly, based on the selective control of noncovalent interactions, guides the creation of hierarchically ordered materials providing access to novel structures and new properties. This field has expanded significantly in the last two decades, and one of the most ubiquitous functionalities is terpyridine. Despite its wide-spread use, much basic knowledge regarding the binding of terpyridine with metal ions remains unknown. Here, the binding constants of PEG-substituted terpyridine in relation to other literature reports are studied and a few examples of supramolecular materials from our laboratory are summarized. [source]

    Shape persistence as a concept in the design of macromolecular architectures

    MACROMOLECULAR SYMPOSIA, Issue 1 2003
    Gerhard Wegner
    Abstract Shape persistent macromolecules are objects defined by a time independent overall shape. In most cases such macromolecular objects are characterized by an exterior surface structure and an internal architecture giving coherence to the shape and topology. Shape persistent macromolecules are essential to the development of a polymer based nanotechnology and serve as constitutive units of larger scale architectures either via self-organization or via processes in which they are assembled to give constructs of nanoscale defined patterns. [source]

    Nitroxide-mediated radical polymerization of N -ethyl-2-vinylcarbazole

    POLYMERS FOR ADVANCED TECHNOLOGIES, Issue 6 2008
    Jeffrey D. Quinn
    Abstract The hole-transporting ability of carbazole-containing polymers makes them attractive for applications in organic electronics. Nitroxide-mediated radical polymerization (NMRP) offers the potential to create complex macromolecular architectures, including block copolymers, but N -vinylcarbazole, the simplest and most widely studied carbazole monomer, is known to polymerize poorly by NMRP. Here, we investigate the NMRP of N -ethyl-2-vinylcarbazole (2,VK), a monomer structurally more similar to the styrenes which are known to polymerize well by NMRP, and whose polymer offers a hole mobility an order of magnitude higher than poly(N -vinylcarbazole). Polymerization of 2,VK from a unimolecular alkoxyamine shows a molecular weight which increases steadily with time, though termination or decomposition of the "living" radical ends is clearly evident from the progressive formation of a low-molecular-weight tail as conversion increases. However, a sufficient fraction of the chains remain living that P2VK-PS diblock copolymer can be formed by chain extension of the P2VK macroinitiator with styrene. Copyright © 2008 John Wiley & Sons, Ltd. [source]