Effects of pH/temperature on the swelling behavior and rheological properties of hydrogel.

摘要

In order to prepare the colloidal particle filled rubbery composite composed of connections of each particle bridged by one single polymer chain, particle size must be as small as possible, especially below 40 nm in diameter. First, emulsifier free emulsion polymerization of styrene was achieved, but the size range of final particles was about 210 nm to 700 nm in diameter, and it was much bigger than our desired size. Alternatively, microemulsion polymerization of styrene was carried out, and the diameter of final particle was about 40 nm.;Nano-sized polystyrene (PS) particles prepared by microemulsion polymerization were incorporated in pH sensitive poly (acrylic acid) hydrogel (PAG) with varying cross-linking density to produce two types of PS bead filled PAG -- F40PAG by copolymerization, and PAGPS by the addition of PS bead. Comparing with other two types of hydrogels: PAG and PAGPS, F40PAG showed the slowest swelling rate, lowest equilibrium swollen ratio, highest pH sensitivity of equilibrium swollen ratio, highest storage shear modulus and highest yield strength.;When the pH sensitive monomer such as acrylic acid (AAc) or acrylamide glycolic acid (AAmGAc) was introduced into temperature sensitive poly ( N-isopropylacrylamide), it was expected that the phase transition temperature of polymer solution would be observed as a function of pH and the concentration of acid comonomer. In addition to the phase transition behavior, rheological properties, especially viscosities, were also tested and compared.