C. Damian et al., GAS-PERMEABILITY OF MODEL POLYURETHANE NETWORKS AND HYBRID ORGANIC-INORGANIC MATERIALS - RELATIONS WITH MORPHOLOGY, Journal of applied polymer science, 65(12), 1997, pp. 2579-2587
Various polyurethane (PU) and hybrid organic-inorganic networks based
on isocyanate chemistry were synthesized using a two-stage method. All
the networks were amorphous. For PU membranes the morphology and the
permeability coefficients of different gases (H-2, N-2, O-2) were a fu
nction of the polarity and the chain length of the soft segment and a
function of the composition of the networks. The membranes based on th
e same soft segment chain length and on the same molar composition wer
e structurally nanoheterogeneous systems for the less polar soft segme
nts (alpha,omega-hydroxyterminated hydrogenated polybutadiene and a fa
tty acid oligoester). They were homogeneous for a polycaprolactone typ
e soft segment. The gas diffusion was appreciably hindered in the case
of better miscibility between the soft chains and the hard crosslinks
. Decreasing the soft segment length decreased the gas permeability co
efficient of the network. As the chemical compositions were changed by
increasing the soft segment content, an increase in permeability coef
ficients was observed. The morphology and transport properties of PU n
etworks and hybrid organic-inorganic networks with low inorganic conte
nt were compared for the same soft segment content. The similarities o
bserved between the two types of networks led us to conclude that the
organic or inorganic nature of the crosslinking agent has no influence
on the gas transport properties of these networks. (C) 1997 John Wile
y & Sons, Inc.