Syntheses of hydroxypropyl methylcellulose phthalate hydrogels in Na₂CO₃ aqueous solutions with electron‐beam irradiation

Abstract

Novel cellulose ether hydrogels were prepared by the radiation-induced crosslinking of hydroxypropyl methylcellulose phthalate (HPMCP) in a solution of Na 2 CO 3 . The effects of several factors, such as the HPMCP concentration, Na 2 CO 3 concentration, absorbed dose, and dose rate, on the crosslinking of HPMCP were investigated in detail. An increase in the HPMCP concentration resulted in an increasing content of the gel fraction, and this meant that the crosslinking probability increased as well. Na 2 CO 3 was essential for dissolving HPMCP in water, and a 4 -5% Na 2 CO 3 aqueous solution was optimal for the crosslinking of HPMCP. The dose rate also affected the radiation crosslinking of HPMCP; hydrogels with higher gel fractions and transparency could be formed at lower dose rates. The ratio of degradation to crosslinking of the gel was calculated according to the Charlesby-Rosiak equation, and it showed good agreement with the experimental results. Some important properties, such as the swelling kinetics, ion and ionic strength dependence, and pH dependence, of the HPMCP hydrogels were also investigated. The HPMCP hydrogels possessed excellent swelling rates and swelling ratios in some solvents, such as water and methanol, with a high hydrogen-bonding parameter.

Preparation of carboxymethyl sago pulp hydrogel from sago waste by electron beam irradiation and swelling behavior in water and various pH media

“…The chemical gel can be produced by using high‐energy electron beam radiation under mild conditions as paste‐like solutions that do not degrade polysaccharides 23. At lower CMSP concentration, there is also a possibility that the density of the macroradicals produced by the electron beam radiation is not high enough to recombine on different chains and the macroradicals then undergo a radiation degradation reaction 30…”

“…At moderate and high CMSP concentrations, high electron beam dose rate may generate 10 or 100 of radicals simultaneously on each chain. Under these conditions, the probability and yield of intermolecular recombination is greatly reduced and intramolecular recombination occurs preferentially and therefore, reduces the crosslinking and reducing the percentage of gel fractions 30…”

Carboxymethyl sago pulp/carboxymethyl sago starch hydrogel: Effect of polymer mixing ratio and study of controlled drug release

“…Thus, this causes degradation to happen predominantly . Besides, irradiation on a low concentration of polymers will produce insufficient macroradicals and unable to recombine on different chains . The CMSP and CMSS mixtures with higher concentration had higher gel fraction because more free radicals on the side chains of the polymers.…”

Syntheses of hydroxypropyl methylcellulose phthalate gels in organic solvents by radiation crosslinking

“…Figure 1 shows the crosslinking behavior of HPMCP solutions (40 wt %) in methanol, methyl acetate, and acetone. In the case of HPMCP hydrogels, which were prepared from concentrated aqueous solutions,8 the gel fraction rapidly increased after the irradiation dose reached a gelation dose (ca. 50–60 kGy, depending on the polymer concentration), which was defined as the minimum irradiation dose required to obtain gels, and then leveled off.…”

“…Generally, HPMCP is processed after its dissolution in a solution of Na 2 CO 3 to dissociate the carboxyl groups on the polymer and to impart a certain hydrophilicity. Our previous article8 reported the preparation of HPMCP gels by electron‐beam radiation in a solution of Na 2 CO 3 . The prepared gels behaved as polyelectrolyte hydrogels, and the hydrophobicity of the polymer was remarkably reduced.…”