THE PHASE-BEHAVIOR OF TETHERED CHAINS - AN OVERVIEW

Theoretical arguments suggest a rich variety of phase transitions involving grafted chains: (1) The "pancake-cigar" transition occurs in tethered layers consisting of weakly adsorbing grafted chains. This first order transition involves coexistence of uniformly adsorbed and grafted chains. (2) The tilting transition occurs in lamellae formed by rod-coil block copolymers. The orientation of the rods with respect to the lamellar normal evolves via a first order phase transition reminiscent of the S(A)-S(C) transition in liquid crystals. (3) The stretching of a dense brush immersed in a poor solvent involves a first order phase transition. This gives rise to a distinctive f approximately L0 force law associated with the coexistence of a dense, collapsed brush and a dilute brush of stretched chains. (4) Finally a whole family of demixing transitions are predicted. The precise behavior is determined by the operative constraints on the mobility of the chains.