نتایج جستجو برای: polyesters
تعداد نتایج: 2577 فیلتر نتایج به سال:
In this paper, an efficient method for synthesis of aromatic polyesters containing schiff base units is described by preparation of two polyesters. These polyesters have been prepared by the reaction of terephthaloyl dichloride on Schiff bases derived from p-hydroxybenzyldehyde and 4,4-diamino diphenyl ether, 4,4-diamino diphenyl methane. The Polymers were characterized by IR, CHNS, thermal...
A new homologous series of linear aliphatic polyesters, such as poly (cis-2- butenylene carboxylate)S, PBms (m is the number of methylene groups in the acid component, m=2-8 have been synthesized by direct polyesterification reactions in anisole, as solvent. FT-IR, 400 MHz H- NMR, C-NMR and elemental analysis were used to establish the structure of polyesters. Molecular weight distributi...
Three linear polyesters with pendant ketoprofen were synthesized by copolymerization of polyethylene glycol (PEG) with malic acid (thiomalic acid or aspartic acid) using lipase B acrylic resin from Candida antarctica (CAL-B) at 90 °C respectively. These thermosensitive polyesters exhibit a lower critical solution temperature (LCST) at 10–12 °C. The in vitro study demonstrated that these polyest...
The synthesis of novel polyesters from model long-chain aliphatic monomers and from suberin reactive aliphatic fragments was conducted using mild polycondensation or polytransesterification conditions. The ensuing polyesters were characterized by means of various techniques. When mixtures of simple suberin-like monomers were used, the ensuing polyesters had very regular structures, with melting...
Three series of polyalkanoates (adipates, suberates and sebacates) were synthesized using as monomers three sugar-based bicyclic diols derived from D-glucose (Glux-diol and isosorbide) and D-mannose (Manx-diol). Polycondensations were conducted in the melt applying similar reaction conditions for all cases. The aim was to compare the three bicyclic diols regarding their suitability to render al...
Boric acid-pyridine mixture is presented as mild catalyst for polycondensation of semi-esters of ethylene glycol, in situ-generated by “cyclic anhydrideediol” reaction scheme from maleic, succinic and phthalic anhydrides. This catalyst system was demonstrated to give colorless polyesters in low molecular weights (Mn: 1650e1950 Da) within 4 h at 130 C 1H NMR spectra of the polyesters derived fro...
The focus in the field of biomedical engineering has shifted in recent years to biodegradable polymers and, in particular, polyesters. Dozens of polyester-based medical devices are commercially available, and every year more are introduced to the market. The mechanical performance and wide range of biodegradation properties of this class of polymers allow for high degrees of selectivity for tar...
Controlled routes to prepare polyesters and polycarbonates are of interest due to the widespread application of these materials and the opportunities provided to prepare new copolymers. Furthermore, ring-opening copolymerization may enable new poly(ester-carbonate) materials to be prepared which are inaccessible using alternative polymerizations. This review highlights recent advances in the ri...
A microbial fermentation system was designed to convert glucose to 4-hydroxyphenyllactic acid (DHPA), which is an aromaticcontaining derivative of lactic acid. By methylation, DHPA was transformed to a diol monomer for synthesis of bio-based polyesters with benzene rings in their backbone. The polycondensation of the DHPA diol was performed with a series of aliphatic diacid chlorides to produce...
New carbohydrate-based polyesters were prepared from isoidide-2,5-dimethanol (extended isoidide, XII) through melt polymerization with dimethyl esters of terephthalic acid (TA) and furan-2,5-dicarboxylic acid (FDCA), yielding semi-crystalline prepolymers. Subsequent solid-state post-condensation (SSPC) gave high molecular weight (Mn =30 kg mol(-1) for FDCA) materials, the first examples of high...
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