4(%3)3 - Ecole nationale supérieure de chimie de Montpellier

The value of subscripts “n”, “x” and “y” are 795, 319 and 262 respectively. The synthesis of thiscopolymer is based on nitroxide mediated controlled radical polymerization, well described in an earlierwork 20 . We used the copolymer synthesized in collaboration*, in as such form without any furthermodification. The copolymer can essentially be considered as amphiphilic in nature due to presence ofhydrophobic PSAN block and hydrophilic PEO block in the middle. By varying the binary solvent mixturecomposition, nonergodic morphologies like spherical and spider-web were obtained in the previouswork 20 . The relatively hard PSAN blocks (T g > 100 o C) formed the core while the softer PEO (T g < - 40 o C;due to presence of oxygen in the main chain) formed corona of the spherical micelles. Amphiphilic Blockcopolymer like this are known to exhibit nonergodicity which leads to a large variety of micelles’ lockedinmorphologies in accordance to their initial preparation pathways 21,22 . Therefore, we decided to notchange the molecular weight and block ratio.2.2 MEMBRANE PREPARATIONThe 3-dimensional superstructure was prepared from a homogeneous solution of PSAN-b-PEO-b-PSAN in DMF/toluene (50/50 v/v) at a concentration of 100 mg.ml -1 . Analysis carried out using PhotonCross Correlation Spectroscopy (PCCS) showed absence of micelles in the solution, even after increasingthe concentration up to 200 mg.ml -1 . Beyond this concentration, the polymer solution was too viscous tobe analyzed. The homogeneous solution of the copolymer in DMF/Toluene was then spin-coated ontothoroughly cleaned silicon wafers under argon atmosphere for certain duration of time with 20 dropletsper wafer (Figure – 2.2).Figure – 2.2: General representation of preparation of PSAN-b-PEO-b-PSAN copolymer micelles’ membrane films48