Dynamic mechanical analysis-Fourier transform infrared spectroscopy (DMA-FTIR) studies of polymer rheology

The work described in this dissertation is divided into two parts: the first is the description of the development of three novel approaches to step-scan Fourier transform infrared (FT-IR) spectroscopy; the second is a report on the rheo-optical investigation of films of Estane 5703®, a random block copolymer, by use of both rapid- and step-scan FT-IR combined with dynamic mechanical analysis (DMA).; The three methods described in the first of these two parts are as follows: First, a novel but easy way of simultaneous multi-frequency light intensity modulation by use of step-scan FT-IR is developed. Its potential for application to photoacoustic depth profiling of layered polymeric samples is also demonstrated. Secondly, the application of step-scan time-domain spectral measurement (an alternative way to the conventional sinusoidal deformation method) is for the first time applied to the rheo-optical study of polymer films under repetitive impulse deformation of small amplitude. Finally, a new double-modulation method for obtaining static and dynamic orientations of polymer chains under sinusoidal small amplitude strain modulation is developed.; In the second part of this dissertation, DMA-FTIR is applied to studies of an Estane elastomer. The study of the static dichroic data obtained from stepwise stretching and the static and dynamic dichroic data obtained from sinusoidal stretching allow differentiation of the static and dynamic orientation responses of different functional groups. The same study is also applied to Estane samples with various plasticizer concentrations. Temperature-controlled experiments provide an understanding of how glass-transition affects the molecular mobility and thus the viscoelasticity of Estane. Finally, a research-grade desktop DMA is coupled with our research-grade FT-IR spectrometer to allow versatile DMA-FTIR characterizations of polymers. This new development is demonstrated in the creep/recovery study of Estane. A novel approach to quantitative analysis of the orientation functions of different bands by use of the macroscopic viscoelastic model elucidates the microscopic structural origins of the high elasticity and high stability of the network structure of the Estane elastomer.