Network Properties of Ureasil-Based Polymer Matrixes for Construction of Amperometric Biosensors as Probed by PALS and Swelling Experiments

Abstract

Network properties of ureasil-based polymer matrixes suitable for construction of amperometric biosensors were probed by positron annihilation lifetime spectroscopy and swelling experiments. Temperature dependences of the ortho-positronium (o-Ps) lifetimes and their relative intensities were measured in a temperature range of 15-350 K. Glass transition temperatures and expansion coefficients of microscopical free-volume for the investigated polymers were determined. Differences in network behavior for the aged samples and the effect of chalcogenide (As2S3) particles on the free volume of ureasil network were observed. Swelling experiments using ethyl alcohol showed that the structure of the aged sample network had less swelling ability for the pure ureasil as well as composite. This suggests that the one of factors influencing swelling is the change of the basic ureasil network due to ageing. It is supposed that the network properties obtained by positron annihilation lifetime spectroscopy and swelling experiments could be very helpful to understand better the bio-functionality of the constructed biosensor based on the ureasil-chalcogenide glass composite.

Controlling the Network Properties of Polymer Matrices for Improvement of Amperometric Enzyme Biosensors: Contribution of Positron Annihilation

“…) of microscopical free-volume, and swellability S for the ureasil-based polymers are gathered in Table I [2,4]. The incorporation of As 2 S 3 clusters into ureasil matrix results in the decreasing the hole volume V h at glass transition temperature T g and increasing T g , difference (α F2 − α F1 ) of the coefficients for the thermal expansion of free-volume holes α F1 , α F2 below and above T g , respectively, and swellability S.…”

“…Two types of polymers such as an organic-inorganic hybrid ureasilicate (shortened name -ureasil) and a photocross-linked polymer were selected for research. The synthesis of the ureasil-based polymers (pure ureasil and ureasil/As 2 S 3 composite) was reported in [1][2][3][4].…”

“…The temperature dependent PALS experiment was carried out as described in [2]. The lifetime spectra were taken using a 22 Na positron source with activity of 2 MBq and analyzed with the free of charge LT Polymers program.…”

“…The swelling tests were performed during 8 days for the ureasil-based polymers and 2 days for the photocrosslinked polymers at room temperature. Details of swelling experiment were reported in [2,4,5].…”

“…At the same time, positron annihilation lifetime spectroscopy (PALS) is known as a progressive method for microstructural analysis of macromolecular structures. Combination of both methods allowed to get information about network properties of the polymer matrices and the results obtained will be further compared with sensitivity of bioelectrodes constructed using the polymer matrices [1][2][3][4][5]. A role of free-volume and crosslink density in the host polymer matrices used for improvement of operational parameters of laccase-based amperometric biosensors would be established.…”