Hydrophobically modified associating polymers could be effective drag-reducing agents containing weak “links” which after degradation can reform, protecting the polymer backbone from fast scission. Previous studies using hydrophobically modified polymers in drag reduction applications used polymers with M w ≥ 1000 kg/mol. Homopolymers of this high M w already show significant drag reduction (DR), and the contribution of macromolecular associations on DR remained unclear. We synthesized associating poly(acrylamide-co-styrene) copolymers with M w ≤ 1000 kg/mol and various hydrophobic moiety content. Their DR effectiveness in turbulent flow was studied using a pilot-scale pipe flow facility and a rotating “disc” apparatus. We show that hydrophobically modified copolymers with M w ≈ 1000 kg/mol increase DR in pipe flow by a factor of ∼2 compared to the unmodified polyacrylamide of similar M w albeit at low DR level. Moreover, we discuss challenges encountered when using hydrophobically modified polymers synthesized via micellar polymerization.

Large amounts of relatively expensive small-molecule surfactants, between 6 and 25%, are typically required for the formulation of oil/water high or medium internal phase emulsion (H/MIPE) templates. We synthesized an amphiphilic “macrosurfactant” copolymer poly­(acrylamide-co-styrene) via micellar polymerization. As-synthesized poly­(acrylamide-co-styrene) still associated with 0.01 wt % cetyltrimethyl­ammonium bromide (CTAB) can be used to produce stable toluene or cyclohexane-in-water H/MIPEs already at concentrations of 0.1 wt %. Emulsion templates containing 2-hydroxyethyl methacrylate (HEMA) and N,N-methylene­bis­(acrylamide) (MBAm) in the aqueous continuous phase can be polymerized to produce macroporous poly­(HEMA-co-MBAm)­M/HIPEs. Our poly­(HEMA-co-MBAm)­M/HIPEs synthesized in templates stabilized with much lower emulsifier content were mechanically more robust, in dry and swollen state, as compared with poly­(HEMA-co-MBAm)­HIPEs reported in the literature.