A simple one‐step synthesis of unsaturated copolyesters

Abstract

SynopsisCopolyesters containing pendent vinylidine groups were prepared in a one-step synthesis by reacting either chloro-or bromoacetic acid with 2-(bromomethyl)acrylc acid and triethylamine in diethyl ether. Polymers were characterized by IR, 'H-and 13C-NMR, DSC, and TGA. Copolymer formation supports a mechanism involving a triethylammonium carboxylate salt acting as an active nucleophilic species in a manner analogous to that seen in phase transfer catalysis involving carboxylate anions. Comparison of I3C-NMR spectra intensities indicates that 2-(bromomethy1)acrylic acid is much more reactive than the haloacetic acids leading to higher copolymer incorporation than in the monomer feed. Unsaturation in the copolymers provides a site for crosslinking during radical polymerization with an added vinyl monomer, similar to the way unsaturated polyesters function in commercial fiberglass formulations. This was confirmed by polymerization of both styrene and methyl methacrylate in the presence of an unsaturated copolymer giving insoluble semi-interpenetrating networks. These unsaturated copolymers are the first examples of soluble biodegradable glycolic acid polyesters containing such reactive functionality.

Acrylate-containing oligo(ether-ester) cross-linking agents with controlled molecular weights via end-group termination

“…Alternatively, polyesterification generated oligomers of glycolic acid containing randomly incorporated RHMA residues capable of serving as cross-linking sites. 14 We felt it desirable to extend these approaches to more controllable synthesis of new unsaturated polyesters of structure 3.…”

Mechanism study of the base-catalyzed ether formation involving α-(hydroxymethyl)acrylates

“…During the synthesis of a-(hydroxymethyl)acrylate esters 1 using the diazabicyclo[2.2.2]octane (DABCO) catalyzed addition of formaldehyde to the corresponding acrylate,1 it was observed that ether 2 and acetal products 3 and 4 were formed.2, 3 The diacrylate ether was subse-"°~r quently investigated as a cross-linking agent,4 a monomer for cyclopolymerization,5,6 and a comonomer with dithiols for Michael polymerization. 7 An ene-type mechanism for ether formation was proposed2 (Figure 1) involving a six-membered ring transition state with essentially simultaneous transfer of a proton, loss of water, and ether bond formation. It has been determined that base is needed to catalyze the ether-forming reaction.…”