RAFT聚合制备嵌段聚合物结构对降滤失剂性能的影响

为了探究聚合物结构对降滤失剂性能的影响，选用AMPS作为阴离子组分、离子液体1-乙烯基-3-乙基咪唑溴盐（VeiBr）作为阳离子组分及AM作为中性组分，采用可逆加成断裂链转移自由基（RAFT）聚合法合成了一系列组成相同而结构不同的两性离子降滤失剂。通过调节单体加入顺序合成了3种结构精确、键接顺序不同、分子量分布窄且可控的聚合物结构，即无规共聚物、部分嵌段共聚物和完全嵌段共聚物，并评价了其流变性能、降滤失性能。结果显示在其他条件相同的条件下，无规分布聚合物的降滤失效果最好，而嵌段聚合物可用于制备高动塑比的流型调节剂。通过改变链转移剂加量，精确调节聚合物分子量，进一步分析了同一聚合物结构下不同分子量对其性能的影响。结果表明分子量越大，聚合物整体呈现黏度增大、降滤失性能得到改善的趋势。因此，无规序列结构的嵌段聚合物在钻井液降滤失剂中性能较好，同时分子量越大的聚合物更加具有优势，该研究为从结构出发研发高效降滤失剂提供了理论基础。 

Effects of the Molecular Structure of Block Polymer Developed through RAFT Polymerization on Filtration Property of Drilling Fluids

A series of isomeric zwitterionic filter loss reducers have been developed for investigating the effects of the molecular structure of polymers on their filtration control performance. These isomeric zwitterionic filter loss reducers were synthesized through reversible addition-fragmentation chain transfer polymerization (RAFT) with monomers such as AMPS (ionic monomer), 1-vinyl-3-ethylimidazollium bromide (VeiBr, as cationic monomer) and acrylamide (AM, as neutral monomer). By adjusting the sequence of adding different monomers, three copolymers, which are a random copolymer, a partial block polymer and a full block copolymer, respectively. These three copolymers have precise molecular structures, different bonding sequence (of atoms) and narrowly distributed and controllable molecular weights. Laboratory performance evaluation of these copolymers have shown that under the same test conditions, the random copolymer has the best filtration control performance, while the block copolymers can be used to make high YP/PV ratio flow pattern modifiers. By changing the concentration of the chain transfer agent, the molecular weight of the copolymers can be effectively adjusted, and this helps analyze the effects of copolymers with the same molecular structure and different molecular weights. It was found that the higher the molecular weight, the higher the viscosity and the better the filtration control performance of the copolymers. It is thus concluded that block polymers with random sequence structure are more suitable for filtration control in drilling fluids, and polymers with higher molecular weight will perform better in this aspect. This study has provided a theoretical base for developing high efficiency molecular structure oriented filter loss reducers.