Tj Smith

Highly soluble polyimides from sterically hindered diamines

Polyimides with enhanced solubility have been synthesized from various aromatic tetracarboxylic dianhydrides and sterically hindered diamines. Intrinsic viscosities in 1-methyl-2-pyrrolidinone (NMP) ranged from 0.28 to 1.05 dL/g. Most of the polyimides were soluble in common solvents such as N,N-dimethylacetamide, NMP, chloroform and tetrahydrofuran. Polyimides derived from thianthrene-2,3,7,8-tetracarboxylic dianhydride (TDAN) and diamino mesitylene (DAM) or diethyltoluene diamine (DETDA) were insoluble in all solvents indicating that polyimide solubility decreased as anhydride rigidity increased. Glass transition temperatures ranged from 252 to 398°C and above with the polymers showing little or no weight loss by TGA up to 400°C in both air and nitrogen. The glass transition temperatures of the polyimides increased 15 to 98°C (compared to unhindered polyimide analogs) when one or more methyl group was placed ortho to the imide nitrogen, hindering backbone rotation, chain packing and flexibility. Tough, transparent films of the soluble polyimides were cast from solution.

Hyperbranched poly(3-ethyl-3-hydroxymethyloxetane) via anionic polymerization

Abstract Anionic polymerization of 3-ethyl-3-hydroxymethyl oxetane was achieved using NaH with coinitiators benzyl alcohol (BA) or trimethylol propane (TMP). Pendent hydroxyls facilitate a multibranching polymerization. NMR confirmed the presence of linear, dendritic, and terminal repeat units. For TMP initiated polymerizations there was an acetone soluble portion which was more branched (DB=0.48) than the acetone insoluble portion (DB=0.20). Polymers were not soluble in water, ether or THF, but were partially soluble in acetone and completely soluble in methanol, benzene, chloroform, and DMSO. MALDI-TOF analysis showed relatively low molecular weights (around 500) and confirmed the presence of both cyclic and TMP endgroups.

Crosslinking kinetics of methyl and ethyl (α-hydroxymethyl)acrylates: effect of crosslinker type and functionality

Abstract Photopolymerizations were carried out using monofunctional monomers methyl or ethyl-(α-hydroxymethyl)acrylate (MHMA and EHMA, respectively) with multifunctional crosslinkers. The effect of crosslinker type (acrylate versus methacrylate) and functionality (di-, tri-, tetra- and penta/hexaacrylates) on polymerization rates and conversions were investigated. RHMA systems (monomer plus crosslinker) reached very high conversions (70–83%) for all systems with the exception of dipentaerythritol penta/hexaacrylate systems. Network Tg played an important role in final conversions with dipentaerythritol penta/hexaacrylate and pentaerythritol tetraacrylate, while EHMA (with a lower Tg) went to higher conversions than MHMA.