Isodimorphism
and isomorphism are becoming mature approaches but
separately used to regulate crystallization behavior of random copolymers
and thus their performances. Most of the research work is focused
on binary copolymers while leaves random copolymers containing more
than two kinds of comonomeric units rarely studied in which both isodimorphism
and isomorphism may occur together. This experiment is realized in
the terpolymers of poly(butylene adipate-ran-butylene
succinate-ran-butylene fumarate) (PBASF) wherein
butylene adipate (BA) displays isodimorphic behavior with either butylene
succinate (BS) or butylene fumarate (BF), and BF builds an isomorphic
structure with BS. When the BA content is kept almost unchanged at
∼50 mol %, PBASF can be subtly tailored from a pseudoeutectic
state to only isomorphic state by increasing the BF content that suppresses
the crystallizability of the PBA-rich phase but hardly affects the
PBSF-rich phase. Crystallization behaviors of PBASF from both melt
and quenched samples are assayed in detail by using a differential
scanning calorimeter, X-ray diffractometer/scatterometer, and Fourier
transformation infrared spectrometer, and the mechanism of confined
crystallization is clearly unraveled, which is relied on both intersegment
hydrogen-bonding interaction and physical restriction. Furthermore,
a crystal phase diagram for random terpolymer of PBASF is proposed,
which provides an overall guide to tailor its crystallization. This
example of the strategy combining isodimorphism and isomorphism raised
here sheds light on precise regulation of properties and performances
of terpolymer and copolymer with more complicated chain structures.
Big spherulite structure and high crystallinity are the two main drawbacks of poly(butylene succinate) (PBS) and hinder its application. In this work, a new type of copolyester poly(butylene succinate-co-butylene acetylenedicarboxylate) (PBSAD) is synthesized. With the incorporation of acetylenedicarboxylate (AD) units into PBS chains, the crystallization temperature and crystallinity are depressed by excluding AD units to the amorphous region. In contrast, the primary nucleation capability is significantly strengthened, without changing the crystal modification or crystallization kinetics, leading to the recovery of total crystallization rate of PBSAD under the same supercooling condition. The existence of specific interaction among AD units is found to be crucial. Although it is too weak to contribute to the melt memory effect at elevated temperature, the interaction continuously strengthens as the temperature falls down, and the heterogeneous aggregation of AD units keeps growing. When the aggregating process reaches a certain extent, it will induce the formation of a significant amount of crystal nuclei. The unveiled nucleation mechanism helps to design PBS copolymer with good performance.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.