Membrane with organophilic nature, such as Pulydimethylsiloxane (PDMS) membrane is required for separation of organic from aqueous effluents. In this report, PDMS membrane is in-situ modified with hydrophobic alkyl chain by direct cross-linking PDMS liquid precursor with an organochlorosilane having a long alkyl chain viz. n-octadecyltrichlorosilane and trichloro(1H,1H,2H,2H-perflourooctyl)silane in toluene solvent under ambient conditions for enhanced selectivity towards organic than water. Series of membranes were prepared with three different cross-linking densities. The cross-linking density was measured by swelling experiments while the nanoscale structure was probed by SANS and TEM. Cross-linked structure of the membrane was probed by Si-29 NMR measurement. SEM, XRD, DSC, FT-IR, Contact-angle measurements were also used to characterize microstructure morphology, hydrophobicity and other physico-chemical properties of the membrane. The modified PDMS membranes exhibited higher efficiency than performance of the typical PDMS membrane in the removal of dissolved organics from waste water by pervaporation separation. (C) 2015 Elsevier B.V. All rights reserved.