A random walk model of chain polymer adsorption at a surface. II. Effect of correlation between neighboring steps

Abstract

A random walk lattice model of adsorption of an iso la ted polymer c hain at a so lu t ion surface is inves ti gated . The model is a modifi cation of a s imple c ubic lattice in which the re is a co rre la tion between success ive s te ps. The direc tion of each s tep is at right angles to the direc tion of the preceding step (a ll bo nd angles are 90°). O ne-dime nsional c harac te ri s ti cs of the monomer unit di s tribution a re de termined analyti call y in the limit of long polyme r cha ins neglec tin g the self-excluded vo lume. T he mean numbe r of monomer units adsorbed in the surface laye r V(() , N) is de termined assuming th a t one end of the po.lymer chain li es in the s urface layer, where N is the mean nu mber of monome r unit s in the c ha in and () is the adsorption ene rgy of each monomer unit in the surface layer measured in units of kT . In addition, the mean di s tan ce of the free e nd of the cha in from the s urface laye r z(() , N) is dete rmined. Th e properties of thi s corre lated step model a re qualita ti ve ly s imila r to the pro perti es whi ch ha ve been fo und in unco rre la ted s te p models. In pa rti c ula r, there is a c riti ca l va lue of the adsorpt ion ene rgy ()c such that for () > ()c, vii!, N) is proportiona l to N. Num erical va lu es of N'v(() , N) and z( () , N) are p resented for () > ()c = In (V51).