A Brønsted acid is a substance that donates a proton (H+) in a chemical reaction. In polymer chemistry, Brønsted acids can be used as catalysts in various polymerization reactions, such as cationic polymerization. They can initiate the polymerization by protonating the monomer, creating a reactive cationic species. Examples of Brønsted acids include sulfuric acid, hydrochloric acid, and acetic acid.

布朗斯特酸是在化学反应中提供质子 (H+) 的物质。在高分子化学中，布朗斯特酸可用作各种聚合反应（如阳离子聚合）的催化剂。它们可以通过质子化单体来引发聚合，从而产生反应性阳离子物质。布朗斯特酸的例子包括硫酸、盐酸和乙酸。