Effect of the Pore Formation on the Solution Flow through Acrylamide Gel
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ABSTRACT A simple synthesis method of porous acrylamide gel is proposed. Pore formation in gel body is dominated by the amount of polymerization initiator, accelerator and gelation temperature. We investigated the influence of these factors on the number and the size of pores. Gelation temperature control is the easiest and the most effective way to create a number of large pores in a gel body. We also investigated the pore volume fraction dependence of solution flow through the gels. Solution flow rate was found to be promoted with the increase of pore volume fraction. INTRODUCTION Gel actuator is one of the future practical gel products, which has fascinated the people in the field of polymer science for long years. However, it is well known that volume change of gels is so slow, since it is dominated by solution diffusion [1]. Such a property stagnates the realization of gel actuators. Creation of tiny pores in gel body is one method to design faster responsive gels [2, 3], since they will shorten the solution diffusion path. Kabra et.al synthesized porous PVME gels by applying y-ray to the pregel solution and extensively investigated its volume change property [2]. Wu et.al synthesized macroporous polyNIPPAm gels by the use of HPC (hydroxypropylcellulose) as a pore formation agent [3]. They mixed pregel solution with HPC and the HPC was removed from the gel body after the polymerization. Neither method is simple. y-ray radiation method needs y-ray facility, which is not commonly accessible, while HPC method implies a difficulty in removing the HPC from the polymerized gel. In this paper, we propose a simple method of a porous acrylamide gel synthesis and investigate the controlling parameter of pore formation and the solution flow rate through the porous gels.
EXPERIMENT a. Porous gel synthesis and controllability of the pore size and the number porous gel synthesis Porous acrylamide gels were prepared by the following method, where all chemicals were purchased from Aldrich (Milwaukee, WI) and used without further purification. The pregel solution which consists of acrylamide (monomer), N,N'-methylenebisacrylamide (crosslinker), N,NN',N'-tetramethylethylenediamine (accelerator) and deionized water (solvent) is heated up for 30 minutes. Once ammonium persulfate (polymerization initiator) is added to it, immediately the gelation and pore formation started simultaneously and they were completed soon. This method is different from the conventional gel synthesis method that the pregel solution in the present method is heated up completely without adding polymerization initiator [4]. controllability of the pore size and number The number and size of pores are greatly influenced by the amount of polymerization initiator, accelerator and gelation temperature. We investigated these effects on the pore formation. All gel specimens described below were prepared by following the porous gels synthesis procedure described above, and their composition and gelation temperature are summarized in Table 1.
273 Mat. Res. Soc. Sy
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