Crystallization Behaviors and Structure Transitions of Biocompatible and Biodegradable Diblock Copolymers

Abstract

Biocompatible and biodegradable block copolymers (BBCPs) containing crystalline blocks become increasingly important in polymer science, and have great potential applications in polymer materials. Crystallization in polymers is accompanied by the adoption of an extended conformation, or often by chain folding. It is important to distinguish between crystallization in homopolymers and in block copolymers. In homopolymers, chain folding leads to metastable structures introduced by the crystallization kinetics. In contrast, equilibrium chain folding in diblocks can be achieved as the equilibrium number of the folds is controlled by the size of the second block. The structures of BBCPs, which are determined by the competition between crystallization, microphase separation, kinetics and processing, have a tremendous influence on the final properties and applications. In this review, we present the recent advances on crystalline-crystalline diblock copolymer in our group.

Block Copolymers of Macrolactones/Small Lactones by a “Catalyst-Switch” Organocatalytic Strategy. Thermal Properties and Phase Behavior

“…With the literature showing a complex phase behavior for block copolymers, − it was essential to ascertain the thermal properties to understand the phase behavior of PMLs- b -PSLs block copolymers. The T c , T m , and melting enthalpy (Δ H m ) of each component were determined using DSC.…”

Effect of Composition on the Crystallization, Water Absorption, and Biodegradation of Poly(ε-caprolactam-co-ε-caprolactone) Copolymers

“…The formation of small spherulites is beneficial for PCL to maintain its high toughness. Besides, the ring-banded spherulites were observed for C 50 -co-A 50 , which depend on the chemical composition and the crystallization of PA6 [20,21].…”

“…The formation of small spherulites is beneficial for PCL to maintain its high toughness. Besides, the ring-banded spherulites were observed for C50-co-A50, which depend on the chemical composition and the crystallization of PA6 [20,21]. Some research work [5,11,12] also involves the crystallization behavior of P(CLA-co-CLO) copolymers, but because it is difficult for PCL blocks to crystallize in most case for their synthesized copolymers, the influence of PA6 blocks on the crystallization behavior of PCL blocks has never been discussed.…”

Manipulation of Crystallization Sequence in PEO-b-PCL Films Using Solvent Interactions

“…In most copolymers, the crystallization occurs in a sequential manner due to the vast difference in melting temperatures ( T m ) of each block. − The initial nucleation of one block leads to imperfect or confined crystallization of the other, therefore resulting in a structure that is more crystallized with the first block. ,,− When strongly segregated materials undergo microphase separation, this structural element also influences the crystallization and the macroscopic behavior. − Thermodynamically, the stability of the amorphous melt for the high T m block decreases more rapidly during cooling, leading to crystal nucleation and subsequent growth of those crystals prior to nucleation of the second block. The lower T m block crystallizes after further cooling, typically at a temperature much lower than the first block, either in a microphase-separated domain in strongly segregated block copolymers − or between the lamellae of the crystals formed by the higher T m block (weakly segregated or miscible). − For these more common CC block copolymers, the macroscopic properties are derived primarily from the higher T m polymer crystals and hierarchical organization. Control over the crystallization processes is difficult because the window to manipulate morphology, crystallinity, and other structural aspects that govern properties is limited and isolated to each individual block.…”