Structural and kinetic modification of aqueous hydroxypropylmethylcellulose (HPMC) induced by electron beam irradiation

Kazuya Furusawa, Toshiaki Dobashi, Satoshi Morishita, Mikio Oyama, Tadashi Hashimoto, Naoki Shinyashiki, Shin Yagihara and Naotsugu Nagasawa

Physica A: Statistical Mechanics and its Applications, 2005, vol. 353, issue C, 9-20

Abstract: Aqueous solutions of 10 and 20wt% hydroxypropylmethylcellulose (HPMC) were irradiated with different doses to make gel films. The gel fraction of the film increased sharply above a critical dose upon increase of the dose and then decreased gradually after passing a maximum. The scission/cross-linking ratio and the critical dose were determined with the aid of Charlesby–Rosiak equation as 0.52 and 9kGy for the 10wt% gel and 0.43 and 14kGy for the 20wt% gel, respectively. The gel fraction for the 20wt% HPMC film was lower at low dose and higher at high dose than that for the 10wt% film. The behavior of the swelling ratio of the gel film was just opposite to that of the gel fraction. The cross-linking density of the gel estimated from the Flory theory increased linearly with the irradiation dose at low dose, passed through a maximum around 100 and 160kGy for 10% and 20% films, respectively, and decreased at high dose. These results suggest a competition of scission and cross-linking induced by the indirect effect of irradiation. Dielectric-relaxation measurements by time-domain reflectometry and RF impedance/material analyzer revealed two characteristic relaxations of chain motions around 100MHz and of orientation of free water around 20GHz. From the dose dependence of the dielectric-relaxation parameters determined by fitting to a combined equation of the Cole–Cole type and of the KWW type, a coupling of motions of HPMC molecules and water molecules was strongly suggested. The critical dose for gelation was coincident with the dose for the maximum of τh and the minimum of Δεh together with the minimum of τm and the maximum of Δεm, where τh and Δεh denote the relaxation time and the relaxation strength for water molecular motion and τm and Δεm the corresponding ones for HPMC molecular motion. The characteristic behavior is discussed in terms of an increase of the affinity between HPMC and water and the constrained molecular motion in the gel network.

Keywords: Hydroxypropylmethylcellulose (HPMC); Electron beam irradiation; Gel fraction; Swelling; Dielectric spectroscopy; Coupled molecular motion (search for similar items in EconPapers)
Date: 2005
References: View complete reference list from CitEc
Citations:

Downloads: (external link)
http://www.sciencedirect.com/science/article/pii/S0378437105000580
Full text for ScienceDirect subscribers only. Journal offers the option of making the article available online on Science direct for a fee of $3,000

Related works:
This item may be available elsewhere in EconPapers: Search for items with the same title.

Export reference: BibTeX RIS (EndNote, ProCite, RefMan) HTML/Text

Persistent link: https://EconPapers.repec.org/RePEc:eee:phsmap:v:353:y:2005:i:c:p:9-20

DOI: 10.1016/j.physa.2004.12.068

Access Statistics for this article

Physica A: Statistical Mechanics and its Applications is currently edited by K. A. Dawson, J. O. Indekeu, H.E. Stanley and C. Tsallis

More articles in Physica A: Statistical Mechanics and its Applications from Elsevier
Bibliographic data for series maintained by Catherine Liu ().