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Phase behavior and transreaction studies of model polyester/bisphenol-A-polycarbonate blends
Abstract
The goal of this thesis is to quantitatively study the relationship between interchange reaction and blend phase behavior in polyester/bisphenol-A-polycarbonate (PC) blends. Before transreaction studies are conducted, equilibrium phase behavior prior to reaction is identified and used as a basis to judge the reacting blends. To facilitate all of these studies, poly(2-ethyl-2-methyl-1,3-propylene terephthalate) (PEMPT) has been selected as a model polyester for blends with PC. PEMPTs having M$\sb{\rm n}$s from 4,100-37,500 g/mol were synthesized and fully characterized by a variety of elemental, spectroscopic and thermal analysis techniques. In addition, PEMPT was end capped to produce samples having heptafluorobutyrate (HFB) and benzylate (BNZ) end groups. These end capped samples exhibit different thermal characteristics compared to the hydroxyl (OH) terminated PEMPTs. Blends of PEMPT with PCs having M$\sb{\rm n}$s of 11,000 and 21,000 g/mol were prepared by solution casting techniques. Equilibrium phase behavior studies were conducted as a function of blend composition, molecular weight and end group type. In most cases, PEMPT/PC blends exhibited partial miscibility, which was monitored by the shifting of glass transition temperatures as measured by DSC. Blend composition had little effect on the phase behavior. Molecular weight reduction lead to improved intermixing between components for the OH and BNZ terminated PEMPTs. No improvement in the degree of intermixing was observed with decreasing M$\sb{\rm n}$ in the HFB terminated PEMPT/PC blends. Detailed $\sp1$H NMR spectroscopy enabled the identification of separate resonances corresponding to direct midchain and alcoholysis interchange reactions in PEMPT/PC non-stabilized blends. It was found that transreaction of $\sim$4% of the terephthalate groups was required to shift the phase behavior from two phase to single phase in a PEMPT/PC 50/50 wt. % blend of high molecular weight. This reaction extent represented 2.8% alcoholysis and 1.2% direct midchain reaction. These results were in agreement with calculations based on simplified models of the reacting blend. Alcoholysis exchange reaction was also observed at varying degrees in stabilized blends. Complete alcoholysis led to the formation of single phase blends at low PEMPT molecular weights.
Subject Area
Chemical engineering|Polymer chemistry
Recommended Citation
Kollodge, Jeffrey Scott, "Phase behavior and transreaction studies of model polyester/bisphenol-A-polycarbonate blends" (1992). Doctoral Dissertations Available from Proquest. AAI9305851.
https://scholarworks.umass.edu/dissertations/AAI9305851