Structure-property correlation in cyclopolymerization of new acrylate-based functional monomers

Huseyin Tas

Abstract

New ether dimer; (ED-Od) and (ED-Eh) and diester; (ODE) and (EHDE) derivatives of α-(hydroxymethyl)acrylate, each having two octadecyl and 2-ethylhexyl side chains respectively, and an amine-linked di(2-ethylhexyl)acrylate (AL-Eh), having three 2-ethylhexyl side chains, were synthesized and (co)polymerized to evaluate the effects of differences in the structures of the monomers on final (co)polymer properties, particularly glass transition temperature, Tg . The free radical polymerizations of these monomers yielded high molecular weight polymers. Cyclopolymer formation of ED-Od, ED-Eh and AL-Eh was confirmed by 13 C NMR analysis and the cyclization efficiencies were found to be very high (∼100%). Copolymers of ED-Od, ODE, ED-Eh, EHDE, and AL-Eh with methyl methacrylate (MMA) showed significant Tg decreases over PMMA due to octadecyl and 2-ethylhexyl side groups causing 'internal' plasticization. Comparison of the Tg 's of the copolymers of octadecyl methacrylate, ED-Od, ODE and 2-ethylhexyl methacrylate, ED-Eh, EHDE, and AL-Eh with MMA revealed that the impacts of these monomers on depression of T g 's are identical with respect to total concentration of the pendent groups. That is, the magnitude of decrease in Tg 's was quantitatively related to the number of the octadecyl and 2-ethylhexyl pendent groups in the copolymers rather than their placement on the same or randomly incorporated repeat units. A new member of the readily available family of α-functionalized acrylates has been synthesized, characterized, and polymerized. Reaction of 2-ethylhexyl acrylate with paraformaldehyde in the presence of catalytic 1,4-diazabicyclo[2.2.2]octane (DABCO) and t -butyl alcohol at elevated temperatures leads to ca. 30% yields of 2-ethylhexyl α-(hydroxymethyl)acrylate (EHHMA). Continued reaction leads to ca. 75% conversion to the ether dimer of this compound. Copolymerization with styrene occurs readily to give products that appear to be essentially random copolymers based on the reactivity ratio values of the monomers. Compositions of copolymers prepared in low conversion by bulk polymerization of EHHMA and styrene were determined by 1 H NMR and 13 C NMR spectroscopy. Reactivity ratios for both EHHMA and styrene, determined by the methods of Fineman-Ross and Kelen-Tudos, were found to be about 0.42. The depression in the Tg 's of the styrene copolymers with increasing EHHMA content showed a non-linear behavior which was attributed to the competition of a plasticizing and an anti-plasticizing group located within EHHMA structure. The acrylamide (ACRCL), methacrylamide (MACRCL), diallyl (DAAC), and diacrylate (DEMAC and ED-ACL) derivatives of α-amino-ε-caprolactam were synthesized. The monomers were obtained with good conversions and high purity. Free radical polymerizations of DAAC, DEMAC, and ED-ACL gave soluble cyclopolymers due to high degree of intra- rather than intermolecular reactions during polymerizations. 1 H NMR and 13 C NMR analyses of the cyclopolymers confirmed that the cyclization efficiencies were very high. All homopolymers showed unusually high glass transition temperatures along with unique secondary thermal transitions which were attributed to strong intra- and intermolecular hydrogen bonding.