FT-IR imaging of polymer dissolution

FT-IR imaging was also used to study the dissolution of three types of polymers: (1) entangled poly(α-methylstyrene) (PAMS) in mixtures of two good solvents, (2) poly(methyl methacrylate) (PMMA) in mixtures of either two good solvents or a good solvent and nonsolvent, and (3) symmetric diblock copolymers of poly(styrene-b-methyl methacrylate) in neutral solvents, a selective solvent, a nonsolvent, and mixtures of the selective solvent and nonsolvent. FT-IR images and concentration profiles were obtained.; The results for the entangled PAMS in mixtures of methyl isobutyl ketone (MIBK) and deuterated cyclohexane (C₆D₁₂) were compared and contrasted with the results of the previously reported unentangled system. In many of the solvent mixtures, the solvent did not dissolve the polymer uniformly at the polymer-solvent interface, causing cracking and roughening of the polymer edge. In addition, there was evidence of solvent segregation, which was not seen in the unentangled PAMS.; The PMMA was dissolved in solvent mixtures of MIBK and toluene and also solvent-nonsolvent mixtures of toluene and deuterated methanol (CD₃OD). The dissolution rates were calculated from the concentration profiles and were the same for the various solvent-solvent mixtures, but solvent segregation was observed. In the solvent-nonsolvent mixtures, higher nonsolvent concentrations produced higher dissolution rates with the nonsolvent segregating relative to the solvent.; Three different molecular weights of the diblock copolymer were tested with two individual neutral solvents, toluene and benzene. The dissolution mechanism was governed by either solvent diffusion, resulting in stress cracking for low molecular weights, or disentanglement of the polymer chains, resulting in normal dissolution for higher molecular weights. In addition, benzene dissolved the block copolymer faster than toluene.; The low molecular weight diblock copolymer was also tested with a selective solvent for PMMA (2-ethoxyethanol), a nonsolvent for both polymers (cyclohexane) and mixtures of these solvents. The 2-ethoxyethanol dissolved the copolymer, and swollen, gel and liquid layers were observed. The dissolution rate of the block copolymer was higher with mixtures of the selective solvent with the nonsolvent than for the neat selective solvent, but it decreased with increased weight percent of the nonsolvent.