Synthesis and Characterization of Poly(l-lactide)−Poly(ε-caprolactone) Multiblock Copolymers

Abstract

New poly(L-lactide) (PLLA)-poly( -caprolactone) (PCL) multiblock copolymers were prepared by using the coupling reaction between the bischloroformates of carboxylated PLLA with PCL-diol in the presence of pyridine. All the copolymers were characterized by 1 H NMR and GPC and investigated further by using DSC, TGA, SAXD, WAXD, polarizing microscope, and Instron testing. The molecular weights of PLLA-PCL multiblock copolymers produced lay in the range 40 000-50 000. The multiblock copolymers produced exhibited only one melting peak, corresponding to the PLLA phase, even at a relatively high PCL content, whereas the PLLA-PCL-PLLA triblock copolymers had two melting peaks. The tensile moduli and strengths of the triblock copolymer were very high. On the other hand, the multiblock copolymers were flexible and elastic with relatively good mechanical properties. These copolymers behaved like thermoplastic elastomer due to the presence of physical cross-linking and strain recoveries of more than 95% at 100% strain. Degradation of the copolymers was investigated in PBS for up to 150 days. The random copolymer was found to be rapidly degraded, while the triblock and multiblock polymers were slowly degraded. The molecular weight of the multiblock copolymers decreased with time, but there were no significant changes in their chemical compositions. From 1 H NMR studies, chain scission occurred in the PLLA blocks.

Effect of the molecular weight on the crystallinity of PCL-b-PLLA di-block copolymers

“…Moreover, copolymers based on PLLA and PCL show shape memory properties [19][20][21]. Jeon et al have reported the synthesis and mechanical, thermal and degradability characterization of both homopolymers and tri-block, multiblock and random PCL-PLLA copolymers [22]. Castillo et al reported that the nucleation process and the morphology of both blocks depends on the percentage of them in the copolymer [23].…”

“…In fact, it is known, that the degree of crystallinity and thermal properties of these homopolymers depends on molecular weight [25][26][27][28]. Thus, in copolymers where there are interactions between both blocks, the molecular weight of each block plays an important role on their thermal behaviour [22,23]. To understand these phenomena, a wide series of well-defined PCL-b-PLLA di-block copolymers were synthesized, varying the length of the blocks as well as the relative content of each block.…”

Synthesis of Propargyl-Terminated Heterobifunctional Poly(ethylene glycol)

“…, and the characteristic peak of ester bond is a little stronger at 1760(ν C=O ) cm α-carboxyl-ω-propargyl PEG (2) was prepared with succinic anhydride in the presence of DMAP and triethylamine (TEA) according to literatures [21,22]. According to Figure 4, which shows the 1 H NMR spectra of α-carboxyl-ω-propargyl PEG, appearance of the proton signals of CH 2 formed by the reaction with succinic anhydride at 2.75 is obvious, whereas other proton signals almost remain unchanged.…”

Synthesis and characterization of a novel amphiphilic poly (ethylene glycol)–poly (ε-caprolactone) graft copolymers

“…[1][2][3][4][5][6][7][8][9][10][11][12][13][14][15] PEO is widely used not only for its hydrophilicity and biocompatibility, but also for some properties of POE present in the materials modified by POE. [6] Among the investigated amphiphilic block copolymers, the biodegradable copolymers are of special interest.…”