Dielectric and rheological measurements are reported on the effect of cure temperature on the water absorption of tris[(2,3‐epoxypropoxy)phenyl] methane cured with a 1 : 1 stoichiometric ratio of 4,4′‐diaminodiphenylsulphone. Analysis of the water absorption characteristics of these materials using a combination of dielectric and gravimetric measurements has indicated that water molecules can be found in two distinctly different types of environments. There are water molecules which are strongly interacting with polar groups and water molecules clustered together into sub‐micro‐scale cavities within the matrix structure. Changes in the final cure temperature have the effect of changing both the extent and distribution of the types of water molecules present in the matrix. Validation of the diffusion coefficients obtained from the dielectric analysis is based on a comparison with gravimetric data and the implications are discussed. Differences observed between these two different types of measurement are related to peculiarity in the dielectric method and its extreme sensitivity to interfacial phenomena.
The effect of structure, composition, and cure on the water absorption and Tg of amine‐cured epoxies was investigated. Water absorption is considered to depend on the polar group concentration and type, and on the amount of free volume in the polymer network. The contribution of polar groups in terms of their hydrogen bonding capabilities is reflected by the effect of meta (with respect to the diglycidylamino group) chloro, bromo, and methyl substituents on the water absorption of bis[N,N‐bis(2,3‐epoxypropyl)‐4‐aminophenyl]methane cured with 4,4′‐diaminodiphenylsulphone. The observed water absorptions are in line with the expected electronic effects of the substituents on the basicity of the amine group. Substituents in the ortho position adversely affect the hydrogen bonding capability of the amine group and limit the extent of reaction by steric interference. Examination of four O‐glycidyl systems (Epon 825, Epon 1153/114, Epon 1031, and Dow XD‐7342) cured with 4,4′‐diaminodiphenylsulphone has revealed quite a good linear relationship between the equilibrium water absorption and Tg for a particular hardener concentration irrespective of the epoxy compound employed. Networks ranged from those of low Tg (110°C) and water absorption (1.3%) to those of high values (300°C and 6.1%) for these parameters. Differences in slope for low (50‐65%) and high (100%) stoichiometric amounts of hardener are attributed to differences in the relative importance of OH/epoxy and NH2 or NH/epoxy reactions. The theoretical polar group concentrations and polar group type are much the same for these different systems and thus, free volume is considered to be a function of Tg and to play an important part in determining the level of water absorption.
The use of the Williamson reaction to prepare polyfluoroethers, [OArOCH2(CF2)3CH2]n from 1,1,5,5‐tetrahydryl‐F‐1,5‐pentanediol and polyfluoroaromatic and polyfluoroheteroaromatic compounds was investigated. Fluorine NMR spectroscopy was used to determine the structures of the resultant polymers. F‐Biphenyl and 1,5‐bis(F‐2‐pyridyloxy)‐1,1,5,5‐tetrahydryl‐F‐pentane (BPFP) afforded the polymers where Ar is 4,4′‐C6F4C6F4 and
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respectively. The polymer prepared from F‐pyridine differed from that obtained from BPFP in that it had an irregular structure and contained 2,4′‐ as well as 2,2′ ‐ and 4,4′‐linked rings. F‐Benzene, 4‐(1,1‐dihydryl‐F‐butoxy)‐F‐pyridine, and F‐pyrimidine each gave materials having copolymer structures. The inherent viscosities of the polymers depended on the polyfluorocyclic compound used and ranged from 0.05 to 0.2 dl/g. The heterocyclic polymers were elastomeric. The polymers from F‐pyridine and BPFP had the lowest glass transition temperatures (∼−10°C), and started to lose weight (by thermogravimetry) at ∼300°C in oxygen and at ∼350°C in nitrogen.
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