Synthesis and characterization of the biomaterial poly(lactic acid‐co‐N^ε‐carbobenzoyloxy‐L‐lysine) via direct melt copolymerization

Abstract

With D,L‐lactic acid and Nϵ‐carbobenzoyloxy‐L‐lysine [Lys(Z)] as the starting monomer material and tin dichloride as the catalyst, the drug carrier material poly(lactic acid‐co‐Nϵ‐carbobenzoyloxy‐L‐lysine) was synthesized via direct melt polycondensation. The copolymer was systematically characterized with intrinsic viscosity testing, Fourier transform infrared spectroscopy, 1H‐NMR, gel permeation chromatography, differential scanning calorimetry, and X‐ray diffraction. The influences of different feed molar ratios were examined. With increasing molar feed content of Lys(Z), the intrinsic viscosity, weight‐average molecular weight, and polydispersity index (weight‐average molecular weight/number‐average molecular weight) gradually decreased. Because of the introduction of Lys(Z) with a big aromatic ring into the copolymer, the glass‐transition temperature gradually increased with increasing feed charge of Lys(Z), and all of the copolymers were amorphous. The copolymers, with weight‐average molecular weights from 10,500 to 6900 Da, were obtained and could reach the molecular weight level of poly(lactic acid) modified by Lys(Z) via the ring‐opening polymerization of the cyclic intermediates, such as lactide and morpholine‐2,5‐dione. However, a few terminal carboxyl groups might have been deprotected during the polymerization reaction under high temperatures. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Design, synthesis, and characterization of a potential flame retardant poly(lactic acid‐co‐pyrimidine‐2,4,5,6‐tetramine) via direct melt polycondensation

“…It can be seen that, compared with the homopolymer PDLLA, most copolymer samples have smaller molecular weight. This indicates that the introduction of PTA as a monomer containing the reactive amino is not beneficial to the direct melt copolymerization, and this conclusion is similar with the reported before . However, only sample C3 has bigger M n and M w than PDLLA synthesized under the same reaction conditions, this is related to the formation of multi‐core structure in copolymer, which will be discussed in the following.…”

Synthesis and characterization of a novel drug-loaded polymer, poly(lactic acid-co-aminomethyl benzimidazole)

“…Firstly, different catalysts, such as protonic acid, metal oxides, and metal halides are screened (Table 1). It can be observed that, among five available catalysts usually used in the direct melt homo-/co-polymerization of LA, [28,31,37,40,44] the reaction catalyzed by stannous oxide (SnO) gives the biggest molecular weight (run 2). Thus, SnO is selected as the catalyst in the following experiments.…”

Synthesis and characterization of a novel flame retardant, poly(lactic acid-co-3,3′-diaminobenzidine)

“…According to the previous works on melt copolymerization of LA [18][19][20][21][22], LA and DAB should be prepolymerized before copolymerization. After LA and DAB were uniformly mixed as preplanned molar feed ratio, the mixture was directly dehydrated for 8 h at 140°C under 4000 Pa in a flask equipped with mechanical stirring and thermometer.…”

“…There are many compounds used as catalysts in LA melt polymerization, e.g. proton acids, metal oxides, metal halides, and so on [21][22][23][24][25][26][27]. Here, five common compounds are selected as catalysts, and their influences on the reaction are shown in Table 1.…”

“…Meanwhile, both the single peak phenomenon of all GPC curves and the lower PDI value (less than two) show that the product of direct melt copolycondensation from two monomers is indeed a copolymer P(LA-co-DAB) and not a mixture containing any homopolymer PDLLA. However, due to the partial LA conversion into lactide which can easily escape out of the reaction systems during the direct melt copolycondensation [18][19][20][21][22], the tested LA content in the copolymer is lower than that in the feed ratios. For the same reason, the yields (21-38%) of P(LA-co-DAB)s are also slightly lower ( Table 5).…”