The polycondensation of L-aspartic acid (1) with various ω-amino acids (2) using phosphoric acid catalyst produced poly(succinimide-co-ω-amino acid)s (3), which was followed by alkali hydrolysis to poly(aspartic acid-co-ω-amino acid) (4). The Ca2+ chelating abilities of 4 depended on the content of comonomer unit in the copolymer and on the kind of amino acids. For the copolymer using 11-aminoundecanoic acid (2d) as a comonomer, the Ca2+ chelating ability was higher than that of poly(sodium acrylate). For poly(aspartic acid-co-6-aminocaproic acid) (4c), there was a tendency to increase according to the increase of 6-aminocaproic acid (2c) unit in the copolymer. The biodegradability of the copolymer in the case of 2c as a comonomer, evaluated by TOC measurement, was 63%, which was the highest degradability among the copolymers having different methylen length. The biodegradability of 4c decreased with increasing the 2c unit in 4c. 相似文献
When single crystals of 6-aminocaproic acid (ACA) are heated about 30°C below their melting point, polycondensation to nylon 6 takes place. The polymer crystallites are biaxially oriented towards each other and the relation between their orientation and that of the parent monomer crystal has been clarified. The kinetics of the process are characterized by three stages, (a) an induction period, (b) a stage in which monomer disappears at a constant rate while polymer of relatively low molecular weight is formed, and (c) a slow polycondensation of the polyamide chains after exhaustion of the monomer. Oligomer concentrations were below detectable limits at all stages of the process. Addition of monomer to the polyamide was retarded when ACA was kept from reaching its equilibrium vapor pressure (0.12 mm Hg at 170°C) by condensation on a cool surface or when an inert gas was admitted to the system. This was interpreted as suggesting that ACA is transported through the vapor phase to the propagating polyamide. A number of surfaces catalyzed the polycondensation of ACA vapor, but nylon 6 formed in this way on KCl crystals exhibited no preferred orientation. The linear dimer and trimer of ACA were also found to condense to nylon 6 in the crystalline state, although at a slower rate than the monomer. The solid-state polycondensation of these oligomers was accelerated when they were exposed to the vapor of the monomer. Solid-state polycondensation of single crystals of the linear dimer led also to biaxially oriented nylon 6. 相似文献
The random copolymers of glutamic acid (LG) and aspartic acid (ASP), poly(LG-co-ASP), with designed compositions could be successfully synthesized via combination of N-carboxyanhydride ring opening copolymerization with debenzylation. Ring opening copolymerizations of y:benzyl-L-glutamate N-carboxyanhydride (BLG-NCA) and β-benzyl-Laspartate N-carboxyanhydride (BLA-NCA) were carried out by using different amines including triethylamine (TEA), diethylamine, n-hexylamine (NHA), triphenylamine, diphenylamine or aniline as initiators. All the 6 amines were highly efficient to get well-defined poly(BLG-co-BLA) copolymers with designed compositions although the polymerizations proceeded via different mechanisms (normal amine mechanism or/and activated monomer mechanism), which are based on chemical structure of amines. The molecular weights of poly(BLG-co-BLA) copolymers could be mediated by both TEA concentration and polymerization time. Then, debenzylation ofpoly(BLG-co-BLA) copolymers was conducted to prepare the corresponding hydrophilic random eopolymers of poly(LG-co-ASP) with a-subunit structure in ASP structural units. The contents of LG structural units in poly(LG-co-ASP) copolymers matched with those of BLG-NCA in NCA-monomer feeds in ring opening copolymerizations initiated by NHA or TEA and were closed to the theoretical line. The diblock copolymer of poly(BLG-b-BLA) could also be synthesized via living NCA ring opening copolymerization by sequential addition of BLG- NCA and BLA-NCA. 相似文献
Summary: We report on various synthetic procedures for the preparation of biodegradable and biocompatible poly(lactide-co-aspartic acid) block copolymers based on natural monomeric units – lactic acid and aspartic acid. Multiblock poly(lactide-co-aspartic acid) copolymers of different comonomer composition were synthesized by heating a mixture of L-aspartic acid and L,L-lactide in melt without the addition of any catalyst or solvent and with further alkaline hydrolysis of the cyclic succinimide rings to aspartic acid units. Diblock poly(lactide-co-aspartic acid) copolymers with different block lengths were prepared by copolymerization of amino terminated poly(β-benzyl-L-aspartate) homopolymer and L,L-lactide with subsequent deprotection of the benzyl protected carboxyl group by hydrogenolysis. The differences in the structure, composition, molar mass characteristics, and water-solubility of the synthesized multiblock and diblock poly(lactide-co-aspartic acid) copolymers are discussed. 相似文献
Three types of copolymers of poly(L ‐lactic acid) (PLLA) were synthesized by direct polycondensation of L ‐lactic acid and phenyl‐substituted α‐hydroxy acids (L ‐phenyllactic acid and D ‐ and L ‐mandelic acids). It was found that the glass transition temperature of the copolymers comprising L ‐mandelic acid became significantly higher (from 58 to 69 °C) with increasing content of L ‐mandelic acid (from 0 to 50 mol‐%) although the Mw decreased (from 87 000 to 4 000 Da). The cast films of the L ‐mandelic acid containing copolymers showed improved tensile properties compared with those of the PLLA film. This may be due to a pinning effect of the L ‐mandelic acid units on the helix formation of PLLA, although 30% of the units were racemized. The enzymatic degradability of the L ‐mandelic acid containing copolymers was much higher than that of PLLA, as analyzed with Proteinase K® originating from Tritirachium album.
Synthesis of copolymers of L ‐lactic acid and phenyl‐substituted α‐hydroxy acids. 相似文献
Random copolymers of N-isopropylacrylamide (NIPA) and 4-vinylphenylboronic acid (VPBA) were obtained by solution polymerization using 2,2′-azobisizobutyronitrile as the initiator in ethanol at 65 °C. NIPA-co-VPBA copolymer exhibited both temperature- and pH-sensitivity. Thermally reversible phase transitions were observed both in the acidic and alkaline pH region for the copolymers produced with different VPBA/NIPA feed ratios. The pH dependency of the lower critical solution temperature (LCST) was stronger for the copolymers produced with higher VPBA feed concentrations. RNA was selected as a model biomolecule having vicinal-diol and amino groups that were potentially reactive with the boronic acid groups of NIPA-co-VPBA copolymer. The effect of RNA concentration on the LCST of NIPA-co-VPBA copolymer was investigated in aqueous media at different pHs. Although no significant effect was observed at pH 4, 7 or 10.5, the LCST decreased linearly with increasing RNA concentration at a pH approximately equal to the pKa of boronic acid. This behavior was explained by considering the binding of RNA onto the copolymer chains to occur via two types of complex formation. For the formation of these complexes, the amino and vicinal-diol groups of RNA should react with the boronic acid groups of the copolymer in the tetrahedral anionic form. The results indicated that NIPA-co-VPBA copolymer could be utilized as a new reagent for the determination of RNA concentration in aqueous media. The proposed method was valid for the RNA concentration range of 0–4 g · mL−1.
The schematical representation of the possible interactions between NIPA-co-VPBA copolymer and RNA. (A) A typical structure of single-stranded RNA. (B) Tetrahedral anionic form of boronic acid groups. (C) The interaction between the amino groups of the unpaired bases of RNA and the boronic acid groups of the copolymer. (D) Cyclic borate ester formation by the interaction between vicinal diol groups located at the 3′-end of RNA and boronic acid groups of the copolymer. 相似文献
N-Hydroxysuccinimide-type soluble copolymer with styrene and three similar divinylbenzene (3–4 mole-%) crosslinked copolymers with styrene, N-vinylpyrrolidone, and N,N-dimethylacrylamide were prepared from their precursor copolymers of N-acetoxymaleimide. Acylation of these N-hydroxyl polymers with carbobenzoxyoligo-?-aminocaproic acids was conducted in dimethylformamide at room temperature by using dicyclohexylcarbodiimide as condensing agent. The soluble styrene copolymer was acylated in good conversions (76–89%) in every case (n = 1–3), whereas the acylation of the crosslinked copolymers decreased slightly from n = 1 to n = 2, and dropped suddenly to only small conversions (4.7–7.4%) with n = 3, showing a marked inhibitory effect of crosslinking when the acids became longer. The effect of the microenvironment of the polymer did not appear significant. All the acyl polymers, including the precursor polymers, yielded the corresponding cyclohexylamides when treated with cyclohexylamine. 相似文献
Vapor of 6-aminocaproic acid (ACA) at a pressure of 0.12 mm Hg was observed to polymerize when placed in the presence of different types of surfaces, crystalline and amorphous, at temperatures around 170°C. Two clearly distinct stages of the process could be detected. The first was an induction period, during which the polymer phase must be nucleated. The length of this nucleation stage depended on factors not well understood. In the second stage, polymer was produced at a constant rate which seemed to be related to the vapor pressure of ACA. The polymer produced consisted of the characteristic radiating arrays of ribbonlike crystals known as spherulites. The spherulites, in turn, were made up of primary and secondary lamellae about 90 Å thick. Electron diffraction studies showed that the polymer chains were folded within the lamellae. Further it was proved by chemical and crystallographic arguments that adsorption and polymerization should be simultaneous processes. 相似文献
Three series of block copolymers, namely, polystyrenecaproamide (I), polystyrenehexamethyleneadipamide (II), and poly(styreneethylene terephthalate) (III), were prepared, and the properties of the copolymers in relation to the block sequence lengths and the compositions were studied. Styrene was polymerized in the presence of aluminum chloride and thionyl chloride to give ω,ω′-dichloropolystyrenes of various degrees of polymerization from 12.0 to 51.0, which were either ammonolyzed to ω,ω′-diaminopolystyrene or hydrolyzed to ω,ω′-dihydroxypolystyrene. ω,ω′-Diaminopolystyre was treated with adipic acid to give the corresponding salts, namely, ω,ω′-diammoniumpolystyrene adipate, which was melt-polymerized either with ε-amino-n-caproic acid to give polystyrenecaproamide (I) or with hexamethylenediammonium adipate to give polystyrenehexamethyleneadipamide (II). ω,ω′-Dihydroxypolystyrene was melt-polymerized with dimethyl terephthalate and ethylene glycol to give poly(styreneethylene terephthalate) (III). All the block copolymers were of high enough molecular weight to be cast or spun into films or filaments. Upon polymerization, the increase of the block sequence of PSt units increased the amide content but decreased the ester content of the resulting copolymers. Also, an increase in n decreased the inherent viscosities of the copolymers at a constant monomer feed fc counted by the polymer equivalent of PSt but increased the inherent viscosities at a constant monomer feed rc counted by the monomer equivalent of PSt. The melting points of the copolymers decreased with increasing n values. Also, an increase in n decreased the densities of I and III but increased the density of II at a constant amide or ester composition Fc counted by polymer units but increased the densities of I, II, and III at a constant amide or ester composition Rc counted by the monomer unit. 相似文献