摘要
用表面张力法研究了十二烷基硫酸钠 (SDS)与不同相对分子质量的聚乙二醇 (PEG)或聚乙烯吡咯烷酮 (PVP)的混合体系 ,实验结果表明SDS PEG或SDS PVP的表面张力 浓度对数 (γ lgc)曲线可以具有拟双平台 (或双拐点 )的特点。定义了聚合物相对分子质量阈值 [MP]这个聚合物结构特征常数 ,并发现实验用聚合物的相对分子质量必须超过该类聚合物的 [MP],其γ lgc曲线才可能呈现双拐点特点。实验结果同时显示SDS PEG体系中PEG的 [MP]为 2 0 0 0～ 40 0 0。具有双拐点的γ lgc曲线对应有两个表面活性剂临界浓度值c1和c2 ,且满足c1<CMC <c2 的关系。对同一类聚合物而言 ,当实验用聚合物的相对分子质量超过该类聚合物的 [MP]时 ,在各种聚合物质量浓度和各种聚合物相对分子质量条件下测得的c1值均非常接近。在聚合物具有相同相对分子质量的体系中 ,c2 值随聚合物质量浓度增大而增大 ;在聚合物具有相同质量浓度 (即相同聚合物链节浓度 )的体系中 ,c2
The mixed systems of sodium dodecyl sulfate (SDS) with polyethyleneglycol (PEG) or with polyvinylpyrrolidone (PVP) both with different molecular weights were studied by surface tension. Experimental results showed that there might occur pseudo double-plateau regions or bis-transition points in the γ-lgc curves of SDS-PEG or SDS-PVP. The threshold molecular weight of polymer [MP] is defined as a polymer structure-dependent invariant. Only when molecular weight of the tested polymer is greater than [Mp] can the bis-transition points be found in γ-lgc curve. For example, [Mp] of PEG in SDS-PEG systems is between 2000-4000. Thus, two critical concentration values c1 and c2 could be found along with each γ-lgc curve possessing bis-transition points, which is in keeping with the relationship of c1 less than or equal CMC less than or equal c2. Values c1 are almost independent of molecular weights and concentrations of polymers for a certain type of polymer when the molecular weights of tested polymers are beyond [Mp]. Values c2 increase with the increase in mass concentrations of polymers having same molecular weights, but they depend little on molecular weights of polymers under the same mass concentrations of polymers, that is, the same unit molarity of polymers.
出处
《精细化工》
EI
CAS
CSCD
北大核心
2001年第11期627-630,共4页
Fine Chemicals
基金
高等学校骨干教师资助计划课题 [( 2 0 0 0 ) 6 5 ]~~
