Hydrophobe-containing polymers absorptivities

Aziz et al. [55] advocated that the water absorption of the PDMS elastomers might depend on the surface-treated filler component. Presence of hydrophilic, non-surface-treated silica fillers in the polymer matrix, increase the water uptake of the material (Cosmesil St, Prestige). The presence of -OH groups on the surface of the silica fillers helps to absorb water into the polymer matrix [57]. In the same manner, surface-treated hydrophobic silica filler containing polymer matrixes (Cosmesil HC, A-2186, MED-4920) had negUgible water absorption. The surface groups on these silica particles repel water molecules, and hence prevent water absorption into the material [55]. 

This procedure was designed to provide a measure of the absorptivity of the hydrophobic monomer through the use of a model. The use of a monomeric model compound to represent equivalent chromophores attached to polymer molecules was recently reported for polystyrene 15, 16). UV methods were also used in the determination of copolymer composition and reactivity ratios for isocyanate-containing acrylate polymers (IT). 

The PFCB-PBl polymer was thermally stable up to 358 °C, and the 10% decomposition temperature (T iq) was 493 °C under nitrogen. It was less stable compared to meta-PBl (stable up to 450 °C). Also, the TGA of these PBIs revealed that the PFCB-PBl containing the perfluorocyclobutyl functional group has low water absorption compared to the meta-PBI. The weight losses up to 120 °C due to the loss of water for PFCB-PBl and meta-BBl were 4% and 15-18%, respectively. This is due to the hydrophobic nature of the perfluorocyclobutyl functional group, which decreased the hydrophilicity of the PFCB-PBl polymer [37]. 

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