Dielectric and Optical Properties of Polymer Confined in Random Porous Matrices
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0899-N09-11.1
Dielectric and Optical Properties of Polymer Confined in Random Porous Matrices Fouad M. Aliev Department of Physics, University of Puerto Rico, San Juan, PR 00931-2343, USA
ABSTRACT We report the results of the investigations of the influence of confinement on the glass transition and dynamics of the α-relaxation processes in poly(octylmethacrylate) (POMA) by dielectric spectroscopy. The polymer was synthesized directly in pores of the porous glass matrix with interconnected and randomly oriented pores with an average pore size of 100 nm by free radical polymerization of the monomer. We found that confinement is resulted in the reduction of the glass transition temperature Tg of the polymer. This change in Tg was mainly due to the existence of a developed pore wall-polymer interface and difference in the dynamic behavior of polymer in the surface layers compared to that in the bulk. Complementary light scattering experiments show that in 100 nm matrices containing the polymer an anomalous change in light scattering, which switches the composite from the opaque state to the transparent, in a narrow temperature range around T ≈ 60 oC . These changes could be explained by assuming that at low temperatures (opaque state) the orientational order of the relatively long linear aliphatic side groups is induced by the inner pore surface. The assumption of the formation of the orientationally ordered regions at the pore wall in confined POMA is in agreement with the molecular structures of the polymer and the surface of silica.
INTRODUCTION The synthesis and investigation of polymers in porous matrices with a developed pore surface are of considerable interest because the difference between the surface and bulk properties of polymers may vary greatly in these systems [1-9]. This results from the dispersion of the impregnating polymer on the nanoscale, thereby magnifying the role of the interface between the polymer and the matrix. In microheterogeneous polymer-porous glass systems, the impregnating polymer may be in the colloidal degree of dispersion, and the role of the interface becomes very great. Thus, it is possible to vary the characteristics and structure of the material over a wide range. Polymer-porous glass systems show promise as nanocomposites for optical applications [4,5,9]. In this paper we report on the influence of confinement on glass transition in poly(octyl methacrylate) (POMA) synthesized directly inside the pores of porous silica glass with random pores as investigated by dielectric spectroscopy. The results for confined polymer are compared with those of bulk POMA. Both samples (porous matrix with polymer inside pores and bulk polymer) were prepared in the same container in which the reaction of polymerization was carried out. We restrict our consideration to the results for α-relaxation, which provide information on glass transition and light scattering
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for confined POMA. Due to limited length of this paper the analysis, of the results on βrelaxation process will be p
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