ACRYLATE-CONTAINING OLIGO(ETHER ESTER) CROSS-LINKING AGENTS WITH CONTROLLED MOLECULAR-WEIGHTS VIA END-GROUP TERMINATION

A novel new family of oligomers containing ether and ester groups in the backbone plus pendent vinylidine moieties was obtained through a straightforward and inexpensive reaction between bisacrylate esters and paraformaldehyde. The reaction was catalyzed by 1,4-diazabicyclo[2.2.2]octane. Initial formation of alpha-hydroxymethyl derivatives of the acrylate groups was followed by ether formation involving coupling of two of these groups. End-group analysis indicated variable molecular weights (depending on reactant ratios and reaction conditions) that were difficult to control. More important, higher oligomers underwent phase separation during attempted cross-linking of styrene, and gave nonuniform products with methyl methacrylate. Oligomer formation could be controlled through the addition of ethyl or tert-butyl acrylate, which stopped the growing chains to give terminal ester units. These materials (at the 5% level) gave clear, hard, insoluble products with no phase separation for both styrene and methyl methacrylate bulk thermal and photoinitiated polymerizations. Incorporation at levels up to 50% was examined with methyl methacrylate. While rate of polymerization and gelation increased with increasing oligomer concentration, strength and toughness decreased. Characterization involved FTIR and solution C-13 NMR spectroscopies for reactive oligomers, and FTIR and solid-state C-13 CP/MAS NMR spectroscopies for insoluble products.