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Crystallinity in quasi‐alternating cycloolefin copolymers: Overcoming brittleness
Author(s) -
Moon Seung Hyun,
Park Kyung Lee,
Baek Jun Won,
Lee Hyun Ju,
Choi JiHwan,
Lee Yeonju,
Lee Bun Yeoul
Publication year - 2020
Publication title -
journal of polymer science
Language(s) - English
Resource type - Journals
eISSN - 2642-4169
pISSN - 2642-4150
DOI - 10.1002/pol.20200045
Subject(s) - copolymer , norbornene , materials science , crystallinity , differential scanning calorimetry , polymer chemistry , glass transition , ethylene , amorphous solid , polymer , melting point , polymerization , chemical engineering , composite material , crystallography , thermodynamics , chemistry , organic chemistry , catalysis , physics , engineering
Cycloolefin copolymers (COCs, which are produced via ethylene/cycloolefin copolymerization) and cycloolefin polymers (COPs, which are synthesized by a rather complicated two‐step process via ring‐opening metathesis polymerization and subsequent hydrogenation) are commercialized materials used especially widely in optical applications. Although a COP can be used after processing into a film, films made from conventional COCs are too brittle. Optical‐grade COCs and COPs are generally known as amorphous polymers. By contrast, here, a quasi‐alternating ethylene/norbornene copolymer (norbornene content 56 mol%), prepared from a constrained‐geometry Hf complex, shows some melting ( T m ) signals in a broad temperature range (150–200°C) in the first heating scan of differential scanning calorimetry (DSC) when the samples are prepared by precipitation from a toluene solution. In the second heating scan, only glass transition ( T g ) signals are observed at ~140°C with disappearance of T m signals. The quasi‐alternating ethylene/norbornene copolymer has better mechanical properties (greater elongation at break) than random congeners, which do not show any melting signal, though elongation at break is still inferior to that of the COP which shows the melting signal in the first heating scan of DSC. The enhanced mechanical properties of the quasi‐alternating ethylene/norbornene copolymer and commercial‐grade COP may be ascribed to semicrystallinity observed in the first heating scan.