Modeling and experimental investigation of interdiffusion at compatible polymer interfaces with dissimilar properties
Abstract
In bioadhesion, the biological substrate and the synthetic material can be viewed as macromolecular phases with widely different physical and chemical properties. Therefore, the bioadhesive interface can be modeled by an interdiffusion process at the polymer/polymer interface with dissimilar physical and chemical properties. Previous models for diffusion at polymer/polymer interfaces assume that the monomeric friction coefficient for the two polymers are independent of composition. This assumption is not valid for polymer pairs with dissimilar physical properties. We developed a new model where the free volume theory and the volumetric properties of the blend were used to estimate the composition dependence of the zero shear viscosity for the polymer/polymer pair. The results from the model indicate that the concentration profiles for interdiffusion at dissimilar polymer interfaces are highly asymmetric with substantial swelling of the slower diffusing polymer by the faster moving polymer. A spectroscopic technique was developed for measurement of diffusion at polymer/polymer interfaces based on attenuated total reflection infrared spectroscopy (ATR-FTIR). Experimental results with the model pair PS/PVME indicated that interdiffusion is not dominated by either component and it is controlled by the rate of swelling of the slower diffusing polymer by the faster diffusing one in good agreement with the model predictions. Transmission electron microscopy was used to investigate diffusion at the interface of polymers with similar properties, such as poly(vinyl chloride) and poly(methyl methacrylate). The results indicated that for polymer interfaces with similar physical properties, the concentration profiles were symmetric as opposed to dissimilar polymer pairs which were asymmetric. The ATR-FTIR technique was also used for spectroscopic investigation of diffusion and adhesion at a biointerface consisting of a poly(acrylic acid) (PAA) hydrogel and the mucin component of mucus. The results indicated that, when the PAA and mucin are compatible under the physiological conditions, the mucin swelled the PAA matrix and the extent of adhesion was controlled by the fracture energy of the mucin. This is consistent with model predictions and experimental results of the model pair PS/PVME. (Abstract shortened by UMI.)
Degree
Ph.D.
Advisors
Peppas, Purdue University.
Subject Area
Chemical engineering
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