Surface characterization of the monolayer and Langmuir-Blodgett films of tetra-tert-butyl-copper phthalocyanine

The relaxation and hysteresis phenomena of the tetra-tert-butyl-copper phth alocyanine (ttb-CuPc) monolayer were investigated. The monolayer was then t ransferred to a hydrophilic glass surface to prepare one monolayer of Langm uir-Blodgett (LB) films. The uniformity, stability and molecular arrangemen t of the LB films were studied by measurements of dynamic contact angle (DC A), and were compared with the information obtained by transmission electro n microscopy (TEM) and atomic force microscopy (AFM). The results show that the monolayer of ttb-CuPc is generally stable. The limiting area of a mole cule is smaller than those reported in the literature, which is attributed to the aggregation of ttb-CuPc molecules into multilayer domains. The advan cing and receding contact angles of water on these LB films are much smalle r than those on a homogeneous film prepared by vacuum deposition. The wetta bility analysis on the LB films suggests that ttb-CuPc molecules are not ar ranged uniformly and continuously, and the LB him of ttb-CuPc contains a hi gh ratio of exposed glass substrate. The surface morphology inspected by TE M and AFM shows the formation of separated domains of ttb-CuPc molecules. w hich is consistent with the surface condition evaluated from the surface we ttability. (C) 2000 Elsevier Science S.A. All rights reserved.