Title

Michael-Type Addition Reactions as a Means of Developing Crosslinkable Emulsions

Date of Award

1980

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Polymers and High Performance Materials

First Advisor

B.G. Bufkin

Advisor Department

Polymers and High Performance Materials

Abstract

A feasibility study was conducted whereby the addition reaction between a maleimide acceptor and a nucleophilic donor was investigated as a means of developing crosslinkable emulsions. The suitability of using maleimide acceptors as a means of providing room temperature corsslinkable functionality was established by determining the second order rate constants (k(,2)) for the reaction of N-(n-heptyl)maleimide, N-(n-heptyl)citraconimide, N-(n-heptyl)-3-chloromaleimide, and N-(n-heptyl)-3,4-dichloromaleimide with conventional nucleophilic agents. While all of the maleimide model compounds displayed varying degrees of reactivity at room temperature (the k(,2) values varied from a minimum of 4.14 x 10('0) to a maximum of 2.78 x 10('-5) 1/mole-sec), the 3-chloromaleimido moeity was selected as the most auspicious candidate for the ensuing investigation since the chloro substituent provided a means of sterically protecting the double bond from excessive premature loss during free radical polymerization. In order to prepare an acrylate-type polymer containing pendent 3-chloromaleimido unsaturation, 6-(3-chloro-maleimido)hexyl acrylate (3-CMIHA) was selected as a reasonable candidate for the investigation. To reduce the residence time which 3-CMIHA experienced in the polymerization environment, the model emulsions were prepared using a two-step, delayed addition technique whereby the total amount of 3-CMIHA was added in the last 50 weight percent of the total 60/40-ethyl acrylate (EA)/methyl methacrylate (MMA) monomer feed. Unfortunately, in spite of the methodological and steric measures used to prevent premature loss of the 3-chloromaleimido double bond, analysis for the remaining unsaturation indicated that approximately 40 percent of the initial 3-chloromaleimido functionality was consumed during free radical polymerization. While films containing increasing amounts of 3-CMIHA (up to 12 mole percent) displayed reduced physical properties as a result of the premature crosslinking, coatings of the emulsion containing 2 mole percent (5.31 weight percent) 3-CMIHA demonstrated a 56.7 percent and 31 percent increase in tensile strength and 35 percent and 23.7 percent reduction in elongation with and without the use of an external cross-linking agent (1,6-hexanediamine), respectively; increased solvent resistance; and only moderate losses in impact resistance as compared to a 60/40-EA/MMA control which did not contain 3-CMIHA. When the emulsion containing 2 mole percent 3-CMIHA was combined with various chemically and structurally different curing agents, the coatings cured with m-phenylene-diamine displayed a 93 percent reduction in reverse impact strength, a 160 percent increase in solvent resistance, a 30 percent reduction in elongation, and a 54 percent increase in tensile strength as compared with identical coatings which did not contain a crosslinking agent. In juxtaposition with compositionally similar emulsions crosslinked with conventional types of functionality, 3-CMIHA was rated as being more effective than glycidyl methacrylate but inferior to either N-methylolacrylamide or N-(isobutoxymethyl)acrylamide in providing an overall enhancement of the physical properties of the system.