Biphasic behavior of a thermotropic polymesomorphic polyester. 2. Temperature evolution of phase separation

The temperature evolution of biphase segregation at the N-I as well as S-A- N and S-B-S-A transitions of a main chain polyester I was studied by anneal ing the sample inside the relevant biphasic gaps. The thermodynamic width o f the mesophasic transitions were 2 degreesC for the N-I transition and 6 a nd 4 degreesC for the S-A-N and S-B-S-A transitions, respectively. The maxi mum efficiency of the biphase demixing, in terms of peak resolution, was fo und for the transitions at which the demixing was performed. It was suggest ed that the system lowers its free energy by selective redistribution of sp ecies of different molar masses between two different phases. The analysis of polyester I fractions with different molar masses and molar mass distrib utions showed that the location of the peaks moves to higher temperatures a s the average molar mass increases. In addition, the width of the overall b iphase segregation process was wider for the sample with the widest molar m ass distribution, thus clearly indicating that the molar mass parameters ar e key factors in determining the overall biphase segregation phenomenology.