Chain folding in poly(epsilon-caprolactone) studied by small-angle X-ray scattering and Raman spectroscopy. A strategy for blending in the crystalline state
Sa. Berrill et al., Chain folding in poly(epsilon-caprolactone) studied by small-angle X-ray scattering and Raman spectroscopy. A strategy for blending in the crystalline state, J MAT CHEM, 9(5), 1999, pp. 1059-1063
Samples of poly (epsilon-caprolactone), including narrow fractions obtained
by preparative gel permeation chromatography (GPC), were characterised by
analytical GPC and C-13 NMR spectroscopy. The crystallised samples were inv
estigated by small-angle X-ray scattering to obtain lamellar spacings and b
y low-frequency Raman spectroscopy to obtain LAM-I frequencies. Together th
e two methods gave a reliable estimate of the critical stem length for chai
n folding in poly(epsilon-caprolactone) crystallised at room temperature or
below, i.e. 15 chain units [CL, OCO(CH2)(5)] equivalent to 105 chain atoms
. A necessary requirement for molecular blending of block copolymers of eps
ilon-caprolactone and ethylene oxide with crystalline high molar mass poly
(epsilon-caprolactone) is cocrystallisation. Hence it was concluded that a
safe lower limit for successful blending is a poly(epsilon-caprolactone) bl
ock of 20 CL units.