Method for polymerizing meth(acrylic) acid in a solution, polymer solutions obtained and uses thereof

A method for preparing a (meth)acrylic acid polymer in solution, the polymer having a weight-averaged molecular weight of less than 8000 g/mol and a polydispersity index (PI) between 2 and 5, the method comprising:

• a) introducing water into a synthesis reactor,
• b) heating the reactor to a temperature of at least 60° C.,
• c) introducing the following compounds into the reactor in a continuous and simultaneous manner:
• c1) one or more (meth)acrylic monomers to be polymerized,
• c2) a polymerization initiator system,
• c3) a compound of formula (I):
• wherein X represents Na, K or H, and R represents an alkyl chain comprising 1 to 5 carbon atoms, in an amount such that the mass percentage (weight/weight) between the compound of formula (I) and the one or more (meth)acrylic monomers is between 0.1 and 2.5%, wherein during a) and/or c), sodium hypophosphite NaPO2H2 or a derivative thereof is introduced into the synthesis reactor in a total amount such that the mass percentage (weight/weight) between NaPO2H2 and the one or more (meth)acrylic monomers is between 2.9 and 5.8% by weight.