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Telechelic Polymers (telechelic + polymer)
Selected AbstractsPoly(trimethylene carbonate) from Biometals-Based Initiators/Catalysts: Highly Efficient Immortal Ring-Opening Polymerization ProcessesADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 9 2009Marion 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 of asymmetric telechelic polymers bearing a primary amino end groupJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 10 2006Sunil K. Varshney Asymmetric telechelic polymers bearing a primary amino group on one end and different functional groups, such as thiol, at the other end were synthesized by anionic living polymerization. The anionic initiator was based on a protected primary amine-containing initiator, such as 2,2,5,5-tetramethyl-1-(3-lithiopropyl)-1-aza-2,5-disilacyclopentane. [source] The impact of the concept of "Living Polymers" on material science,POLYMERS FOR ADVANCED TECHNOLOGIES, Issue 9 2007M. Levy Abstract The concept of "Living Polymers" was first introduced in a short communication by M. Szwarc, M. Levy, and R. Milkovich in 1956 and is now widely used in the polymer literature. It led to the synthesis of monodisperse polymers, telechelic polymers, and block copolymers. Living polymerization has evolved in the last 50 years and new methods were developed for various other types of anionic, cationic, ring-opening, and free radical polymerizations. The field has expanded tremendously and the term "controlled/living" polymerization is commonly used to cover all the methods. A few of the interesting developments in the area are described in this paper. Copyright © 2007 John Wiley & Sons, Ltd. [source] | ||||||||||