Miscibility behavior of polyamide 11/sulfonated polysulfone blends using thermal and spectroscopic techniques

Miscibility in a series of blends, derived from Polyamide 11 (PA 11) and su lfonated polysulfone (SPSF) with different sulfonation degrees, 20, 44 and 70% has been investigated using differential scanning calorimetry, dynamic mechanical analysis, Fourier transform infra-red (FTIR) and Raman spectrosc opy. The PA 11/SPSF(Na)(x) blends were prepared by solution casting from di methyl formamide (DMF). Differential scanning calorimetry has shown a melti ng point depression of the equilibrium melting point of PA 11. From the mel ting point data of the blends of PA 11 with the SPSF with a 70% degree of s ulfonation, the value of the polymer-polymer interaction parameter chi(12) was found to be -1.1 at elevated temperatures where it was determined. Less negative values were obtained for the blends of SPSFs with lower degrees o f sulfonation, indicating the role of the sodium sulfonate group to the obs erved miscibility. Dynamical mechanical analysis revealed a non single-phas e system at lower temperatures, although the T-g of PA 11 phase is shifted to higher temperatures. FT-IR and FT-Raman spectroscopic techniques have be en used to confirm the nature of the specific interactions involved. (C) 20 00 Elsevier Science Ltd. All rights reserved.