Stereocomplex Crystallization of Star‐Shaped 4‐Armed Equimolar Stereo Diblock Poly(lactide)s with Different Molecular Weights: Isothermal Crystallization from the Melt

Abstract

The isothermal crystallization of star‐shaped four‐armed equimolar stereo diblock poly(lactide) (4‐LD) polymers with different molecular weights is investigated. Solely stereocomplex (SC) crystallites are formed in all equimolar 4‐LD polymers, irrespective of molecular weight and crystallization temperature (Tc). The wide‐angle X‐ray diffractometry, differential scanning calorimetry, and polarized optical microscopy results for crystalline species, crystallinity, and maximum radial growth rate of spherulites values indicate that both branching and diblock architectures disturb the SC crystallization and spherulites growth of equimolar 4‐LD polymers, and the disturbance effect is larger for branching architecture than for diblock architecture. The equilibrium melting temperature (Tm0) values are 181.9–266.0 °C, which are comparable with or lower than the value reported earlier (279 °C). The crystallite growth geometries of equimolar of 4‐LD polymers are independent of molecular weight and Tc.

Configurational Molecular Glue: One Optically Active Polymer Attracts Two Oppositely Configured Optically Active Polymers

“…In the case of PLA, the mechanical performance, thermal/hydrolytic degradation-resistance of stereocomplexed materials are higher than those of constituent polymers, L-PLA and D-PLA11121314151617. A variety of stereo block343536373839404142434445464748495051, star-shaped5253545556575859606162636465, star-shaped stereo block PLAs6667686970 were synthesized, and the effects of stereo block and star-shaped or branching architectures on crystallization were extensively investigated and found to have crucial effects on stereocomplex (SC) and homo-crystallization behavior.…”

Recent Progress in Using Stereocomplexation for Enhancement of Thermal and Mechanical Property of Polylactide

“…Although the rigidity such as Young’s modulus of PLA could be achieved by simply blending neat PLLA with neat PDLA at equal ratio under certain annealing conditions to form SC PLA, it is, however, at the expense of strength and ductility . Copolymerization of PDLA or PLLA with impact modifiers to produce PLA-based copolymers having various architectures such as block, graft and star has been widely investigated as a technique to achieved good balance between toughness and SC crystallization in PLA. ,, The following sections review the stereocomplexation characteristics of PLA-based copolymers for thermal and mechanical enhancement of PLA in the recent decade.…”

Stereocomplex‐ and Homo‐Crystallization and Phase‐Transition Behavior of Relatively High‐Molecular‐Weight Linear One‐ and Two‐Armed and Star‐Shaped Four‐Armed Poly(l‐lactide)/Poly(d‐lactide) Blends

“…The disturbed SC crystallization during cooling was observed for the higher‐number‐armed PLLA‐ b ‐PDLA copolymers, when compared at the similar total molecular weight . For four‐armed PLLA‐ b ‐PDLA with different l ‐lactyl unit contents and molecular weights, the branching architecture rather than diblock architecture disturbed SC crystallization of equimolar four‐armed PLLA‐ b ‐PDLA and simultaneous SC‐ and homo‐crystallization of nonequimolar four‐armed PLLA‐ b ‐PDLA was inhibited at intermediate l ‐lactyl unit content between 0 and 50% or 50 and 100% …”

“…On the other hand, multiplicate effects of stereo block and branching architectures on SC crystallization were investigated . The disturbed SC crystallization during cooling was observed for the higher‐number‐armed PLLA‐ b ‐PDLA copolymers, when compared at the similar total molecular weight .…”