Synthesis and characterization of block copolymers of styrene‐maleic acid with acrylamide and N,N‐dimethylacrylamide

• Published in: Polymer engineering and science Vol. 62; no. 6; pp. 2031 - 2046
• Main Authors: Khaojanta, Thidarat, Kalaithong, Wichaya, Somsunan, Runglawan, Punyamoonwongsa, Patchara, Mahomed, Anisa, Topham, Paul D., Tighe, Brian J., Molloy, Robert
• Format: Journal Article
• Language: English
• Published: Hoboken, USA John Wiley & Sons, Inc 01.06.2022; Society of Plastics Engineers, Inc; Blackwell Publishing Ltd
• Subjects: Acrylamide; Block copolymers; Chain transfer; Chemical synthesis; Composition; Copolymerization; Copolymers; Hydrolysis; Maleic acid; Maleic anhydride; membrane protein solubilization; Methods; Molecular conformation; N,N‐dimethylacrylamide; Photopolymerization; Polymerization; Properties; Solubilization; Styrenes; styrene‐maleic acid; styrene‐maleic anhydride; Thailand
• ISSN: 0032-3888; 1548-2634
• DOI: 10.1002/pen.25986

Styrene‐maleic acid (SMA) block copolymers with either acrylamide (AM) or N,N‐dimethylacrylamide (DMA) have been synthesized via a 3‐step process comprising: (1) photopolymerization of styrene and maleic anhydride in solution to yield an alternating styrene maleic anhydride (SMAnh) copolymer, (2) copolymerization of SMAnh with either AM or DMA to yield SMAnh‐b‐AM and SMAnh‐b‐DMA block copolymers and (3) hydrolysis of the anhydride groups to yield water‐soluble SMA‐b‐AM and SMA‐b‐DMA block copolymers as the final products. With a view to their intended application in membrane protein solubilization, molecular weights are controlled to below 10,000 by the synthesis conditions employed in step (1), including using carbon tetrabromide (CBr4) as a chain transfer agent. The CBr4 also plays an important role in step (2). By terminating the SMAnh chain radicals from step (1) with C‐Br bonds that are photolytically active, SMAnh chain radicals can be regenerated to act as macroinitiators for the polymerization of AM or DMA in step (2). Finally, following step (3) and due to the pH‐dependency of the SMA chain conformation in solution, a pH of 7–8 is found to be optimal for enabling the final products to be precipitated in a solid form that is completely soluble in water. The synthesis and characterization of some novel styrene‐maleic acid (SMA) block copolymers with acrylamide (AM) and N,N‐dimethylacrylamide (DMA) is described. By careful control of pH during their isolation from aqueous NaOH solution, the SMA‐b‐AM and SMA‐b‐DMA final products were obtained as completely water‐soluble solids. Water solubility is an essential requirement for their intended use in membrane protein solubilization.