Randomly branched bisphenol A polycarbonates. I. Molecular weight distribution modeling, interfacial synthesis, and characterization
✍ Scribed by M. J. Marks; S. Munjal; S. Namhata; D. C. Scott; F. Bosscher; J. A. De Letter; B. Klumperman
- Publisher
- John Wiley and Sons
- Year
- 2000
- Tongue
- English
- Weight
- 172 KB
- Volume
- 38
- Category
- Article
- ISSN
- 0887-624X
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✦ Synopsis
Randomly branched bisphenol A polycarbonates (PCs) were prepared by interfacial polymerization methods to explore the limits of gel-free compositions available by the adjustment of various composition and process variables. A molecular weight distribution (MWD) model was devised to predict the MWD, G, and weightaverage molecular weight per arm (M w /arm) values based on the composition variables. The amounts of the monomer, branching agent, and chain terminator must be adjusted such that the weight-average functionality of the phenolic monomers (F OH ) was less than 2 to preclude gel formation in both the long-and short-chain branched (SCB) PCs. Several series of SCB and long-chain branched PCs were prepared, and those lacking gels showed molecular weights measured by gel permeation chromatography-UV and gel permeation chromatography-LS consistent with model calculations. In SCB PCs, the minimum M w /arm that could be realized without gel formation depended on both composition (molecular weight, terminator type) and process (terminator addition point, coupling catalyst) variables. The minimum M w /arm achieved in the low molecular weight series studied ranged from ϳ3300 to ϳ1000. The use of long chain alkyl phenol terminators gave branched PCs with lower glass-transition temperatures but a higher gel-free minimum M w /arm. SCB PCs where M w /arm was less than ϳM c spontaneously cracked after compression molding, a result attributed to their lack of polymer chain entanglements.