Sequential Polymerization of a Prepolymer Mix

In a polymerization of this type, one or both monomers are first polymerized to form a prepolymer. The two prepolymers are mutually dissolved. Then they are reacted to the network stage more or less sequentially. 

Kim et investigated a system where the principal components were a polyurethane and poly(methyl methacrylate). The synthesis may be briefly outlined as follows  

Materials, The raw materials used are described in Table 5.5. Poly(caprolactone) glycol with average molecular weight of 1978 (Niax D560), 1,4-butanediol (1,4-BD), and trimethylolpropane (TMP) were dried at 60 C for 5 hr under a vacuum of 2 mm. Methyl methacrylate (MMA) was washed with 5% aqueous potassium hydroxide solution, followed by washing with distilled water, dried over Linde 4A molecular sieves, and distilled at 40°C under a vacuum of 2 mm to remove the stabilizer. Trimethylolpropane trimethacrylate (TMPTMA) was also distilled at 40 C under 2 mm vacuum. 4,4 -Diphenylmethane diisocyanate (MDI) and benzoyl peroxide were used without further purification. 

Preparation Polyurethane (PU), The isocyanate-terminated polyurethane prepolymer was prepared by reacting two equivalent weights of 4,4 -diphenylmethane diisocyanate (MDI) with one equivalent weight of poly(caprolactone) glycol (Niax D-560) at 60 C. The prepolymer was stored under vacuum (for not more than two days) because of its susceptibility to 

Niax D-560 Poly(caprolactone) glycol mol wt = 1978, OH No. = 56.7 Union Carbide Corp. 

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