Characterization of the cavity in poly(4-methyl-1-pentene) crystal by gas permeation and 129Xe NMR measurements

Abstract

Characteristic cavity in a crystal part of poly(4-methyl-1-pentene) (PMP) has been investigated by gas permeation and 129Xe NMR measurements for PMP membranes with various crystallinities. For the cavity, permeability coefficients of He, N2, O2, CH4, and CO2 have shown finite values, whereas those of C3H8 and tert-C4H10 have shown zero. From the analysis of 129Xe NMR chemical shifts of 129Xe sorbed in PMP membranes, it has been able to evaluate the size of the cavity in PMP crystal as about 4.5 Å. These findings have indicated that gas molecules less than about 4.5 Å can permeate the cavity in PMP crystal.