Inducing New Crystal Structures through Random Copolymerization of Biodegradable Aliphatic Polyester

Abstract

The crystal structures of poly(hexamethylene sebacate-co-hexamethylene adipate), P(HSe-co-HA), copolymers have been studied with Fourier transformation infrared spectroscopy (FTIR) and X-ray fiber diffraction. All characteristic FTIR absorption bands of the crystals of HSe and HA comonomers are present in all copolymers, and each copolymer has only one melt temperature, which supports that P(HSe-co-HA) copolymers cocrystallize in a whole range of comonomer compositions. In addition to peak shift, some new diffraction peaks were observed in X-ray fiber diffraction patterns of the copolymers, which correspond to new crystals with different unit cells from those of the homopolymers. The crystal structures of the copolymers were analyzed, which varied with the composition of HA and HSe comonomers. Interestingly, the lattice constants c of P(HSe-co-20 mol % HA) and P(HSe-co-35 mol % HA) crystals are even larger than those of either homopolymers, which implies a new length scale may be induced in the random copolymers. This supports the formation of new crystals instead of normal lattice distortion.

Cocrystallization of monomer units in lactic acid-based biodegradable copolymers, poly(l-lactic acid-co-l-2-hydroxybutanoic acid)s

“…P(D-3HB-co-D-3HV)s are reported to crystallize isodimorphically, i.e., 3HV units are partially included into the P(3HB) lattice and vice versa, depending on the monomer composition [42]. Isomorphic cocrystallization is reported for random equimolar copoly(alkylene dicarboxylate) e(eOe(CH 2 ) x eOeCOe(CH 2 ) y-2 eCOe) n -with (x, y) ¼ (2, 10), (2,11), and (2, 12) [43,44], random copoly(alkylene dicarboxylate)s with (x, y) ¼ (6, 10) and (10,6) [43], (6,6) and (10,10) [43], (4,4) and (3,4) [45], (6,10) and (6,6) [46], poly(butylene adipate-co-butylene terephthalate) [47e49], poly(butylene terephthalate-co-butylene succinate-co-butylene adipate) [50], poly(-propylene succinate-co-butylene terephthalate) [51].…”

Synthesis and eutectic behavior of liquid crystalline copolyesters

“…Some conventional copolymers36–43 consisting of A and B units have been reported to exhibit cocrystallization and eutectic melting behavior. In general, cocrystallization behavior in A / B random copolymers can be divided into two types: isomorphism and isodimorphism 37.…”

Preferential Incorporation of Azelaic Acid Units into the Crystalline Phase of the Copoly(Alkylene Dicarboxylate) Derived from 1,9-Nonanediol and an Equimolar Mixture of Pimelic and Azelaic Acids

“…Although melt crystallization of random poly(alkylene dicarboxylate)s have been extensively studied in recent years [16][17][18][19][20][21][22], this is the first time to our knowledge that single crystal morphology of such random copolymers has been evaluated. Figure 4a clearly shows pseudohexagonal lamellae of COPES 9,7/9 with identical morphology and dimensions to those crystals corresponding to the two homopolyesters that are shown in Figures 2c and 3a.…”

“…Incorporation of comonomers has a great influence on the thermal and mechanical properties, sample crystallinity, and both hydrolitic and enzymatic degradability [14][15][16]. Noticeable studies refer to random copoly(alkylene dicarboxylate)s constituted by even units, and specifically representative examples are poly(butylene succinate-co-ethylene succinate) [17], poly(hexamethylene succinate-co-hexamethylene adipate) [18], poly(hexamethylene sebacate-co-hexamethylene adipate) [19,20], and poly(hexamethylene suberate-co-hexamethylene adipate) [21].…”