Phase behavior of functionalized polyolefin solutions and its inference on obtaining membrane by TIPS process

Author(s)

Rosalva dos Santos Marques

• Document type: Doctoral Thesis
• Press: Campinas, SP.
• Institution: Universidade Estadual de Campinas (UNICAMP). Instituto de Química
• Defense date: 2014-09-12

Examining board members

Maria Isabel Felisberti; Juliana Aristéia de Lima; Ana Maria Rocco; Francisco Benedito Teixeira Pessine; Maria do Carmo Gonçalves

• Advisor: Maria Isabel Felisberti

Abstract

The phase behavior of binary and ternary solutions of functionalized poliolefins with hydroxyls (EVOH) and carboxylic acid (PEAA) were studied using dimethylformamide and benzyl alcohol as solvents. PEAA containing 80 mol % and EVOH containing 27 and 44 mol % of ethylene were used. The binary and ternary solutions present a typical UCST behavior associated to liquid-liquid (L-L) and solid-liquid (S-L) phase separation. The temperatures related to L-L and S-L phase separation, TL-L e TS-L, respectively, were determined visually and using DSC, respectively. While TS-L depends on the EVOH solution composition, it is practically constant for PEAA solutions. These results were explained using a model in which the crystallization of PEAA from the solution occurs in absence of solvent, once it involves the polyethylene segments. On the contrary, the crystallization of EVOH from the solution, that involves the hydroxylated segments, occurs in presence of the solvent. This condition leads to the decrease of the chemical potential of EVOH in the solution. The models could be proved by fluorescence experiments using pyrene and uranyl acetate as hydrophobic and hydrophilic probes, respectively. Moreover, the fluorescence experiments allow accessing other transitions not detectable by DSC for ternary solutions. The homogeneous ternary solutions present more than one L-L phase separation by cooling. The ternary diagram was determined by the first L-L phase separation using the composition data accessed by high resolution thermogravimetry. The ternary solutions of all possible combination of polymers and solvents show a restricted miscibility window in the regions near the vertices. The composition of the phases in equilibrium is characteristic of each ternary solution, as well as, the morphology of the materials resulting from the evaporation of the solvent after the solution being subjected to TIPS (Temperature Induced Phase Separation) process. This process applied to binary and ternary solutions resulted in dense or porous materials depending on the polymer-solvent affinity. However, the morphology resulting from ternary solutions subjected to TIPS process and solvent evaporation is unique, showing that the strategy of combining different polymers is a viable route to control the morphology of polymers (AU)

• FAPESP's process: 10/10301-0 - Phase behavior of solutions of functionalized polyolefins and implication in obtaining membranes by TIPS process
• Grantee: Rosalva dos Santos Marques
• Support Opportunities: Scholarships in Brazil - Doctorate