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Research Article

Stress Sensing in Polycaprolactone Films via an Embedded Photochromic Compound

Greg O’Bryan*, Bryan M. Wong and James R. McElhanon*^†

Sandia National Laboratories, P.O. Box 969, Livermore, California 94551, and Sandia National Laboratories, P.O. Box 5900, Albuquerque, New Mexico 87185

ACS Appl. Mater. Interfaces, 2010, 2 (6), pp 1594–1600

DOI: 10.1021/am100050v

Publication Date (Web): May 19, 2010

* Corresponding author. E-mail: gobryan@sandia.gov., †

Sandia National Laboratories.

Section:

Plastics Manufacture and Processing

Abstract

A photochromic polymer exhibiting mechanochromic behavior is prepared by means of ring-opening polymerization (ROP) of ε-caprolactone by utilizing a difunctional indolinospiropyran as an initiator. The configuration of having the photochromic initiating species within the polymer backbone leads to a mechanochromic effect with deformation of polymer films leading to ring-opening of the spiro C−O bond to form the colored merocyanine. Active stress monitoring by dynamic mechanical analysis (DMA) in tension mode was used to probe the effects of UV irradiation on polymer films held under constant strain. Irradiation with UV light induces a negative change in the polymer stress of approximately 50 kPa. Finally, a model of the mechanochromic effect was performed using density functional theory (DFT) and time-dependent DFT (TDDFT) calculations. A sharp increase in the relative molecular energy and the absorption wavelength as well as a drastic decrease in the spiro-oxygen atom charge occurred at a molecular elongation of >39%.

Keywords:

mechanochromic; photochromic; spiropyran; ROP; DFT

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This article has been cited by 2 ACS Journal articles (2 most recent appear below).

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Force-Induced Redistribution of a Chemical Equilibrium
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