Title

Thianthrene and Thioether-Containing Polymers: Monomer and Polymer Formation via Nucleophilic Aromatic Substitution

Date of Award

1994

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Polymers and High Performance Materials

First Advisor

Lon J. Mathias

Advisor Department

Polymers and High Performance Materials

Abstract

Thianthrene-di-, tri-, and tetracarboxylic acids, and a variety of their derivatives, were prepared and polymerized with co-monomers to obtain thianthrene-containing polyimides, amides, amide-imides and benzoxazoles. Thianthrene-2,3,7,8-tetracarboxylic dianhydride was synthesized via nucleophilic aromatic substitution of N-phenyl-4,5-dichlorophthalimide with thiobenzamide, thioacetamide, and sodium sulfide. The imides were hydrolyzed and the acid groups converted to anhydrides. This monomer was then polymerized with aromatic diamines by the conventional low temperature technique to yield soluble poly(amic acid)s. Polyimides were obtained by thermal cyclization of poly(amic acid) films. Rigid diamines gave brittle films whereas 4,4$\sp\prime$-oxydianiline and 4,4$\sp\prime$-methylene dianiline gave films that were creasable. Thianthrene-2,7- and -2,8-dicarboxylic acids plus a synthetic intermediate, 4,4$\sp\prime$-thiobis (3-chlorobenzoic acid), were also synthesized in good yields via nucleophilic aromatic substitution with Na$\sb2$S on N,N-dimethyl-3,4-dichlorobenzamide. New aromatic polyamides having inherent viscosities of 1.29 to 2.39 dL/g were prepared by the direct polycondensation reaction of the dicarboxylic acids with 4,4$\sp\prime$-oxydianiline and 1,4-phenylenediamine in N-methyl-2-pyrrolidinone using triphenyl phosphite and pyridine. Stoichiometric amounts of N,N-dimethyl-3,4-dichlorobenzamide and N-phenyl-4,5-dichlorophthalimide reacted in the presence of Na$\sb2$S did not yield the desired amide-imide thianthrene derivative. However, tri-substituted thianthrene was synthesized by first reacting N-phenyl-4,5-dichlorophthalimide with 3,4-dimercaptotoluene. After deprotecting the imide with base, the methyl group was oxidized with cobalt(II) acetate and oxygen to yield thianthrene-2,3,7-tricarboxylic acid. The thianthrene and thioether dicarboxylic acids were converted to acid chlorides and polymerized with bis-o-aminophenols to yield new thioether and thianthrene-containing poly(benzoxazole)s (PBOs). Polymers were prepared via solution polycondensation in poly(phosphoric acid) at 90-200$\sp\circ$C. Transparent PBO films were obtained directly from polymerization mixtures or cast from m-cresol solutions. The films were flexible and tough. Non-fluorinated PBOs were soluble only in strong acids and AlCl$\sb3$/NO$\sb2$R systems which form complexes with the benzoxazole heterocycle to enhance solubility. Glass transition temperatures of these PBOs ranged from 298-450$\sp\circ$C. Thermogravimetric analysis showed good thermal stabilities in both air and nitrogen atmospheres. New thioether-containing polyimides were also investigated. The polymers were formed via chloro-displacement polymerization of chloro-substituted bisimides by aromatic and aliphatic sulfur nucleophiles. The prepared aromatic monomers and polymers had poor solubility which led to precipitation during synthesis to give low molecular weight polymers. Poly(thioether imide)s prepared from 1,3-propane dithiol and 2-mercaptoethyl sulfide had good solubility but lower thermal stability, showing TGA loss onset temperatures of 297$\sp\circ$C and 298$\sp\circ$C, respectively. A new synthetic technique was used to form poly(thioether imide)s via nucleophilic aromatic substitution of dichloro-substituted bisimides by thiobenzamide. It was soluble and gave a homogeneous mixture of the two monomers. Dichloro-substituted bisimides were prepared from 4-chlorophthalic anhydride and ODA, MDA, neopentyl diamine, and 1,3-phenylene diamine. The polyimides prepared from bisimides containing ODA, MDA and neopentyl diamine had T$\sb{\rm g}$s of 221$\sp\circ$C, 211$\sp\circ$C and 171$\sp\circ$C, respectively. The polymers had good thermal stability, not decomposing till above 400$\sp\circ$C, but inherent viscosities were relatively low. (Abstract shortened by UMI.)