Synthesis of branched polymers via radical copolymerization under oxygen inflow

[Display omitted] •Radical copolymerization of styrene and divinylbenzene in the presence of O2.•Gel-point conversion growth with increasing O2 concentration.•The reaction yields a mixture of linear and branched macromolecules.•Relative amount of highly branched macromolecules grows on approaching to gel point.•In vicinity of gel point, fraction of highly branched macromolecules is 40wt%. Branched and highly-branched polymers were prepared through radical copolymerization of styrene (St) and divinylbenzene (DVB) in the presence of dissolved molecular oxygen (AIBN, 95°С). The gel point (Cg) was found to depend on DVB/St ratio and oxygen concentration in liquid phase ([O2]). Our data of size-exclusion chromatography (SEC) coupled to a multi-angle laser light scattering detector (MALLS) and differential refractive index detector (DRI) suggest that thus synthesized products are a mixture of primary polymer chains (PPCs) and branched macromolecules whose relative amount grows on approaching to Cg. Polymers with a largest amount of highly-branched macromolecules ωHBP≈40wt% were obtained in the vicinity of Cg. Synthesized polymers contain pendant double bonds [CC]≈1×10−3mol/g and some amount of peroxide groups [OO]=(0.1–0.5)×10−3mol/g.