Characterization of Comb Shaped MAA-co-PEGMA Copolymers Synthesized by Free-Radical Polymerization

Methacrylic acid-co-polyethylene glycol methacrylate (MAA-co-PEGMA) copolymers (also known as MPEG-type polycarboxylate ether (PCE) superplasticizers) present comb-shaped microstructure and they are generally used as dispersants of inorganic particles in cementitious formulations. Application properties of the PCEs strongly depend on the molecular structure and therefore accurate characterization of the microstructure is necessary to fully understand the structure–property relationship. In this work, MAA-co-PEGMA copolymers with various lateral size chain lengths and homogeneous copolymer compositions are synthesized by starved-feed semibatch copolymerization. Molar mass and radius of gyration distributions and monomer sequence distribution are measured using size exclusion chromatography coupled with multi angle light scattering (SEC/MALS/refractive index, RI) and ¹H and ¹³C NMR, respectively. Furthermore, it is proved that the experimental radius of gyration compares well with the prediction of a theoretical model for the radius of gyration that uses characteristic parameters of the microstructure of the PCEs (e.g., average molar masses). This confirms the accuracy of the measurements of the absolute molar masses for the MPEG-type PCEs synthesized by free-radical (co)polymerization.