Interaction of surfactant lamellar phase and a strictly alternating comb-graft amphiphilic polymer based on PEG

We study the effect of hydrophobically modified polymers (hm-polymers) on t he phase behavior and membrane elastic properties of the lyotropic lamellar (L-alpha) phase of the nonionic surfactant penta(ethylene glycol) dodecyl ether (C12E5). The hm-polymer is a model comb-graft polymer with monodisper se PEG blocks (loops) of 6, 12, or 35 kg/mol connecting C-18 stearylamide h ydrophobes. The polymer is of interest because both its loops and hydrophob es are biocompatible. The membrane properties are extracted from the small- angle neutron scattering data based on the model of Nallet et al. The monop hasic L-alpha region exists over a narrower membrane volume fraction range but to a higher polymer concentration for hmPEGs with larger PEG spacers. T he rigidity of the membranes increases by 40% with decreasing PEG spacer si ze from 12 to 6 kg/mol or increasing polymer concentration. For hmPEG polym ers with 2-3 loops, the effect of finite chain lengths plays a role on the phase behavior and membrane properties.