Polycarbonate high molecular weight

Polymerization by Transimidization Reaction. Exchange polymerization via equihbrium reactions is commonly practiced for the preparation of polyesters and polycarbonates. The two-step transimidization polymerization of polyimides was described in an early patent (65). The reaction of pyromellitic diimide with diamines in dipolar solvents resulted in poly(amic amide)s that were thermally converted to the polyimides. High molecular weight polyimides were obtained by employing a more reactive bisimide system (66). The intermediate poly(amic ethylcarboamide) was converted to the polyimide at 240°C. 

High molecular weight polycarbonates may be produced without undue difficulty by the phosgenation process. The basic reaction is as shown in Figure 20.5. 

Polybutadienes, polycaprolactones, polycarbonates, and amine-terminated polyethers (ATPEs) are shown in Scheme 4.4 as examples of other commercially available polyols. They are all specialty materials, used in situations where specific property profiles are required. For example, ATPEs are utilized in spray-applied elastomers where fast-reacting, high-molecular-weight polyamines give quick gel times and rapid viscosity buildup. Polycarbonates are used for implantation devices because polyuredtanes based on them perform best in this very demanding environment. Polycaprolactones and polybutadienes may be chosen for applications which require exceptional light stability, hydrolysis resistance, and/or low-temperature flexibility. 

Incorporation of carbon dioxide as a reactive comonomer has been studied by several groups. Inoue et al. were the first to succeed in preparing high molecular weight polycarbonates by the copolymerization of carbon dioxide and propylene oxide241,242 ... 

Requirements for CD-quality material are polycarbonate with low levels of chemical impurities, low particle levels, thermal stability, excellent mold release, excellent clarity, as well as constant flow and constant mechanical behavior (for reproducibility). There exists a time/cost balance. High molecular weight polycarbonate offers a little increase in physical property but the flow rate is slow, making rapid production of CDs difficult. The molecular weight where good mechanical strength and reasonable flow occurs, and that allows for short cycles, is in the range of 16,000-28,000 Da. 

Common to all reinforced plastics are two ingredients, resin and reinforcement. Resin is an oiganic material, usually of high molecular weight, that can be molded and set into a final shape. Resins are of two basic types. Thermoplastic resins soften upon heating, are shaped in a mold, and retain that shape when cooled. Common examples are nylon, polyethylene, polypropylene, and polycarbonate. Thermosetting resins are placed in a mold and cured by the use of a catalyst, heat, or both, until they harden in the shape of the mold. Common examples are polyester, vinyl ester, epoxies, phenolics, and p olyure thanes. 

Materials. Polycarbonate of Bisphenol-A(PC) was a commercial product (Lexan, General Electric Co., U.S.A.), with a viscosimetric average molecular weight Mv = 40,000. High molecular-weight atactic polystyrene (Mv == 280,000) was obtained from Schuchardt, Miinchen. 

As a final example, phenolphthalein (10.38) and related compounds react with phosgene to give high molecular weight linear polycarbonates [1434],... 

Asoh, T. Hosomi, T. Process for Producing Powder Aggregate Particle Formation from High Molecular Weight Polycarbonates European Patent 488,190, June 3, 1992. 

Iyer, V.S. Sehra, J.C. Ravindranath, K. Sivaram, S. Solid-state polymerization of poly (aryl carbonates) a facile route to high-molecular-weight polycarbonates. Macromolecules 1993, 26 (5), 1186-1197. 

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