Polychloroalkane initiators in copper-catalyzed atom transfer radical polymerization of (meth)acrylates

摘要

A series of polychloroalkanes CClnR4-n (n = 2, 3, or 4) was tested as initiators for atom transfer radical polymerization (ATRP) of methyl methacrylate (MMA) and methyl acrylate (MA) using CuCl/2,2'-bipyridine as the catalyst. 2,2-Dichloropropane and 2,2-dichloroethanol initiate the ATRP of MMA very slowly. 1,1,1-Trichloroalkanes, RCCl3, are good initiators. For all the R groups tested, the number-average molecular weight (M) over bar(n) increases with conversion and polydispersities are low (1.1 < (M) over bar(w)/(M) over bar(n) < 1.3). The initiator efficiency factor increases with electrophilicity of the initiating radical (0.7 < f < 1). CCl4 is a multifunctional initiator and the final (M) over bar n values are lower than targeted. This is explained by the generation of new polymer chains occurring once the third active site is creased per chain. ATRP of MA initiated by CCl3CH2CF2Cl or CCl3C8H17 results in polymers with (M) over bar(n) values predetermined by the Delta[M]/[Initiator](0) ratio (f close to 1) and narrow molecular weight distributions ((M) over bar(w)/(M) over bar(n) < 1.3 at high conversion). The polymerization is much slower than that of MMA, but can be considerably accelerated by use of Cu(0) metal while maintaining an excellent control over molecular weights and polydispersities. [References: 36]