Characterization Of Absolute Molecular Weight And Solution Viscosity Of Methacrylate-based Polymer Dispersants

At present,the new type of polycarboxylate dispersants has got more and more application because of their unique dispersion performance.In this paper,the samples of sodiumsaltofmethacrylicacid/acrylicacid-2-isooctyl ester/2-acrylamido-2-methylpropanesulfonic acid terpolymer(SSMAA)with 5wt.%,10wt.%and 30wt.%dosages of initiator(the mass percentage of initiator and monomer)were synthesized via free solution radical polymerization.The properties of polymeric dispersant vary significantly as a function of its molecular weight and polydispersity.The absolute weight-average molar mass(M_w)and polydispersity(M_w/M_n)of SSMAA were successfully determined using aqueous-based gel permeation chromatography coupled with multiangle laser light scattering(GPC/MALLS).We started the research work from screening and optimizing the mobile phase compositions.The results show that mixed solutions of highly concentrated buffered salt and organic solvent modifier are needed to eliminate the interactions between polymer and polymer,and between polymer and stationary phase.Prior to GPC/MALLS analysis,dynamic light scattering(DLS)was firstly used to investigate the aggregation behavior and the particle size of the synthesized dispersant samples in a variety of potential mobile phase compositions and then screen the optimum compositions.The results indicate that the M_w and M_w/M_n values of the three samples prepared with different amount of initiator are 13500,5820,and 2490 g/mol and 1.52,1.45,and 1.47,respectively.The measurement accuracy and precision of the GPC/MALLS method were assessed with the percent relative standard deviation(%RSD),which was contrasted with that of standard material PEG 10K.The%RSD of the synthetic polymer dispersants measurements(0.67-2.01%)is comparable to that of PEG 10K(0.94%),which proves that GPC/MALLS technique is an efficient method to determine absolute weight-average molar mass and polydispersity of this kind of polycarboxylate compounds.The sodium salts of styrene/methacrylic acid copolymer with different molar ratio of monomers were synthesized via solution free radical polymerization,and the absolute weight-average molar mass and solution viscosity of the samples were analyzed.The results show that,the molar ratio of methacrylic acid to styrene(in the range of 2:1-3:1)has little effect on the M_w of the samples.However,the viscosity of the polymer solution tends to increase significantly with increasing the proportion of hydrophobic group styrene.