Critical adsorption of an end-grafted diblock copolymer on a flat surface

Critical adsorption of copolymer tethered on selective surfaces

Critical adsorption behaviors of flexible copolymer chains tethered to a flat homogeneous surface are studied by using Monte Carlo simulations. We have compared the critical adsorption temperature Tc, estimated by a finite-size scaling method, for different AB copolymer sequences with A the attractive monomer and B the inert monomer. We find that Tc increases with an increase in the fraction of monomers A, fA, in copolymers, and it increases with an increase in the length of block A for the same fA. In particular, Tc of copolymer (AnBn)r can be expressed as a function of the block length, n, and Tc of copolymer (AnB)r and (ABm)r can be expressed as a linear function of fA. Tc of random copolymer chains also can be expressed as a linear function of fA and it can be estimated by using weight-average of Tc of different diblocks in the random copolymer. However, the crossover exponent is roughly independent of AB sequence distributions either for block copolymers or for random copolymers.

Critical adsorption of a flexible polymer on a stripe-patterned surface

The adsorption and dynamics of a polymer chain on a stripe-patterned surface composed of periodical attractive and neutral stripes are studied by using Monte Carlo simulation. The critical adsorption temperature Tc and pattern-recognition temperature Tr are estimated from the desorption probability, surface contact number, and bridge number. A phase diagram presenting three polymer states, including a desorbed state above Tc, a multi-stripe adsorbed state at an intermediate temperature Tr < T < Tc, and a single-stripe adsorbed state below Tr, is provided for infinitely long chains. Normal diffusion is always observed for a polymer in the direction parallel to the stripe even at low temperature. But in the direction perpendicular to the stripe, the polymer can freely diffuse above Tc, whereas the polymer is confined to one attractive stripe below Tr. However, the adsorbed polymer can hop from one attractive stripe to another at the intermediate temperature Tr < T < Tc.