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

Crystallization of isodimorphic aliphatic random copolyesters: Pseudo-eutectic behavior and double-crystalline materials

“…Deviations from the linear dependence [19,23,25,28] are typically described according to Fox [29] and Gordon-Taylor [30] equations.…”

“…The pseudo-eutectic behavior of isodimorphic polymers is manifested by a decrease in the transition temperatures with composition departing from those of the two homopolyesters, until a minimum value is reached. The comonomer concentration at which this minimum is found is generally located around the equimolar composition [20,21], however, some systems show pseudo-eutectic points in significantly different concentration interval (e.g., 60:40, 80:20) [4,11,13,16,19,23,36,37]. For instance, in poly (hexamethylene dicarboxilate) copolymers the eutectic composition shifts from a co-unit concentration of 50 to 20 %, with increasing the length of aliphatic diacid units from 4 to 8 CH 2 units [11].…”

Synthesis and stereocomplex formation of enantiomeric alternating copolymers with two types of chiral centers, poly(lactic acid-alt-2-hydroxybutanoic acid)s

“…3(a-c) and summarized in Table S2. † The X c values of unblended P(LLA-alt-L-2HB) and P(DLA-alt-D-2HB) (both nil) are much lower than the puried and meltcrystallized unblended P(LLA-co-L-2HB) random copolymer (56/44) (43.7 and 36.5% for samples, respectively) 75 and puried and solvent-evaporated unblended P(LLA-alt-GA) and P(DLA-alt-GA) alternating copolymers [8.1% and nil for P(LLA-alt-GA) and 7.2 and 4.8% for P(DLA-alt-GA)]. On the other hand, the solventevaporated and precipitated P(LLA-alt-L-2HB)/P(DLA-alt-D-2HB) blends are 66.7 and 60.8%, respectively, which are lower than those reported for the solvent-evaporated and melt-crystallized P(LLA-co-L-2HB) (56/44)/P(DLA-co-D-2HB) (52/48) random copolymer blends (82.5 and 77.7%, respectively), 63 but much higher than those reported for solvent-evaporated and meltcrystallized P(LLA-alt-GA)/P(DLA-alt-GA) alternating copolymer blends (20.8 and 29.2%, respectively).…”

“…All 1 H and 13 C NMR spectra for P(LLA-alt-L-2HB) and P(DLA-alt-D-2HB) are shown in ESI as Fig. S1(a) and S2, † respectively, together with those reported for P(L-2HB), P(LLA-co-L-2HB) random copolymer, and PLLA 75 , the data outside and inside parentheses are for the solvent-evaporated and melt-crystallized samples, respectively], 63 but lower and higher than those for the melt-crystallized PLLA/PDLA homopolymer SC (11.9 , 20.7 , 24.0 ) 78 and P(L-2HB)/ P(D-2HB) homopolymer SC (10.7 , 18.6 and 19.3 , 21.5 ), 79 respectively. The interplanar distance (d) and crystalline diffraction angle (2q) values of samples were obtained from Fig.…”

“…Materials and synthesis (Scheme 1), [69][70][71][72] sample preparation, physical measurements, and observation 62,64,67,[73][74][75] were performed according to the literatures. The details of the experiments are stated in the ESI (Section S1).…”