Photochemical Sciences Ph.D. Dissertations

Smart Polymer Materials

Date of Award

2008

Document Type

Dissertation

Degree Name

Doctor of Philosophy (Ph.D.)

Department

Photochemical Sciences

First Advisor

Douglas Neckers

Second Advisor

Robert Boughton (Committee Member)

Third Advisor

Michael Rodgers (Committee Member)

Fourth Advisor

John Cable (Committee Member)

Abstract

Photochromic superabsorbent polymers with a hydrophilic core and a photochromicshell were prepared by inverse suspension polymerization using acrylic acid (AA) and acrylamide (AM) as monomers, potassium-persulfate as the initiator, N, N'-methylene bisacrylamide (BIS) as a crosslinker, sorbitan monostearate (Span60) as the dispersant,cyclohexane as the solvent and bis(methacryloylamino)-azobenzene (AC) as the photochromic surface cross-linker. The polymer was characterized by NMR, infrared spectroscopy, thermogravimetric analysis and differential scanning calorimetry.

The influence of the polymerization parameters on the properties of the SAPs, water absorption (Q), morphology of the SAPs, swelling kinetics, salt resistance, and the reversibility of water absorption were investigated. The prepared SAPs have excellent water absorption, rapid water uptake, and good resistance to NaCl solutions.Furthermore, they show better reversible water uptake than the previously reported SAPs.

The average water absorbency is 2800 g/g and 181 g/g of liquid absorbance in 0.025 M NaCl solution. The initial water uptake rate is 1357 g/g/min and the reversibility of water absorption is 200 g/g in the repeated fourth cycle. The polymer is stable up to 210 0C. When the sample is irradiated at 350 nm water expulsion from the swollen PSAPs was observed.

Two new easily polymerizable dithienylethene compounds have been synthesized, analyzed and tested in polymerization. The new materials 1,2-Bis(5-ethyleneyl-2- methylthien-3-yl)cyclopentene (DT1) and 1,2-Bis(5-(2-methylprop-2-enoyl)-2- (methylthien-3-yl)cyclopentene (CT2) were obtained by incorporating polymerizable functional groups (ethyleneyl and methacryloyl) at the 5 and 5' positions of the thiophene rings in a diarylethene structure. Both compounds act as photochromic materials. Color occurs reversibly by irradiating with UV and with visible light respectively. Thermal stability, fatigue resistance and polymerizability for both compounds were analysed. Both derivatives can be easily incorporated into polymer matrixes by either photo-curing or radical polymerization. Polymer materials incorporating DT derivatives undergo reversible color changes upon irradiation with UV and visible light respectively. The photochromic films were applied in an erasable recording photon mode.

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