STEM LENGTH AND STEM LENGTH DISTRIBUTION OF CHAIN-FOLDED LAMELLAR CRYSTAL GROWN FROM DILUTE-SOLUTION OF CIS-1,4-POLYISOPRENE BY OZONOLYSIS-GPC MEASUREMENTS

Lamellar crystal of natural rubber (NR), deproteinized natural rubber (DPNR), transesterified natural rubber (NR-TE) and synthetic cis-1,4-p olyisoprene was grown from 0.2% (w/v) hexane solution at the temperatu re between -50 and -70 degrees C. The stem length and stem length dist ribution of the lamellar crystals were investigated by gel permeation chromatography (GPC) and supereritical fluid chromatography (SFC) of t he ozonolysis products. The stem length (L) was detected as the number of isoprene units of ozonolysis products. A broader stem length distr ibution ranging from 2-mer to 13-mer in the single traverse element wa s found for the solution-grown crystal, suggesting an irregular struct ure of the lamellar crystal of the polymer. The stem length distributi on of NR was narrowed by transesterification due to the decomposition of branching of NR. The equilibrium melting temperature was determined to be -17.5 degrees C from a plot of melting temperature versus inver se stem length, for the solution-grown crystal of transesterified DPNR .