| Soluble acrylic copolymers have been widely used in many applications. Copolymers in solid state with significant advantages, such as convenience for delivery and storage, high active content, are of importance in industries. They have been paid more and more attention in recent years. So it is significant to study soluble acrylic copolymers in solid state and their properties. In the paper, soluble acrylic copolymers were synthesized by instant polymerization and inverse suspension polymerization (ISP). The effects of synthesis conditions on the system stability of polymerization process, as well as the water solubility, viscosity and molecular weight of obtained copolymers, were discussed.In some cases the instant polymerization was violent, which could lead to crosslinkage and affect the solubility of products, if it was not controlled well. The different parameters of reaction conditions, such as monomer concentration, initiator, neutralization degree and molecular weight control agent, would affect many properties including the solubility, the viscosity and the molecular weight of copolymers obtained. It was shown in the experimental result that the AA-AM-AN-MA copolymers synthesized by instant polymerization had the excellent solubility, the stable viscosity and the high solid content, under the best reaction condition using monomer concentration 30%~35%, K2S2O8 0.5% (on theweight percentage of monomer), neutralization degree 80% and molecular weight control agent 5.5 X l0-2molL-1 Also low molecular-weight soluble AA-AM-BA copolymers in solid state were synthesized by instant polymerization, and effects of such conditions as monomer concentration, initiator system and neutralization degree on molecular weight were investigated.Inverse suspension polymerization was another method by which the soluble copolymers in solid state were available. Soluble AA-AM-AN-MA copolymers in solid state were prepared by inverse suspension polymerization using cyclonexane as the continuous phase, Span-80/Tween-80 as dispersant and Na2S2O8 as initiator. Some reaction conditions for the system were investigated, like dispersant concentration, HLB value, the ratio of water to oil (O/W), the reaction time, the reaction temperature, amounts of monomer and initiator, and neutralization degree. They could seriously affect many properties such as stability for the reaction system, average particle size, yield and molecular weight of copolymers. So a optimized procedure condition was presented, it included the dispersant concentration 3%, HLB value 4.8, the ratio of water to oil 3/1, the neutralization degree 65%, the reaction temperature 70 , the monomer concentration 50%, and Na2S2O8 0.5% (on the weight percentage of monomer). In the comparison of the instant polymerization with the inverse suspension polymerization it was concluded that the former had the shorter reaction time, the higher reaction rate, the lower energy loss and the higher efficiency. However, the latter had some features including the easy control of reaction and following treatment.Based on structure analysis and properties determination of copolymers it was found that the reaction was a real copolymerization, the resulting copolymers had no any crosslinkage, and their grass transition temperature was 106. It was also found that the products were typical polyelectrolyte, the viscosity of which was sharply affected by factors such as added salt, pH, temperature, storage time and so on. The low molecular weight AA-AM-BA copolymers synthesized by the instant polymerization were a kind of polymeric surfactant, and for its aqueous solution the surface tension could be as low as 41 .OmN/m.
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