Hyper-strained PMMA Uniaxial-Meta-Crystals by Precipitous Quenching with Entropy Diluents
발표자
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초록
내용
Metastable crystalline PMMAs are prepared not only from stereoregular iso- and syndiotactic PMMAs but also from atactic-PMMAs (Mn = 35-1500 kg/mol) by precipitous quenching of molten PMMA/benzoic acid solutions. PMMA chains are extended upto 60-80% of their contour length when they are co-melted with benzoic acid. Upon quenching, PMMA chains are further stretched and form uniaxially orientated crystalline structures due to tensile stress induced by volume shrinkage of benzoic acid. After removing benzoic acid by sublimation, PMMAs show strong birefringence and large residual stress which are much higher than the maximum values that can be obtained by mechanical stretching. Melting temperatures are determined for both s-PMMA and a-PMMA by DSC. Crystal structures are characterized using GIXD. Because of high crystallinity (55~65%) and residual stress, the prepared PMMA show very large storage and rubbery plateau moduli which are 20-160 times higher than those of pristine PMMA.