Film Formation of Nano-Sized Hard Latex (PS) in Soft Polymer Matrix (PBA): An Excimer Study

This work reports steady state fluorescence (SSF) technique for studying film formation from pyrene (P)labeled nano-sized polystyrene (PS) and poly(n-butyl acrylate) (PBA) hard/soft latex blends. Blend films were prepared from mixtures of PS and PBA in dispersion. Eight different blend films were prepared in various hard/soft latex compositions at room temperature and annealed at elevated temperatures above glass transition temperature (T(g)) of polystyerene. Monomer (I(P)) and excimer (I(E)) intensities from P was measured after each annealing step to monitor the stages of film formation. The evolution of transparency of latex films was monitored using photon transmission intensity, I(tr). Film morphologies were examined by atomic force microscopy (AFM). The results showed that as the amount of hard component (PS) in the blend is decreased, a significant change occurred in both I(E)/I(P) and I(tr) curves at a certain critical weight fraction (50 wt%) of PS hard latex. Two distinct film formation stages, which are named as void closure and interdiffusion were seen in (I(E)/I(P)) data above this fraction. However, below 50 wt% PS no film formation was observed. AFM pictures also confirmed these findings. Void closure and interdiffusion stages for (50-100) wt% range of PS were modeled and related activation energies were determined. There was no observable change in activation energies confirming that film formation behavior is not affected by varying the blend composition in this range. POLYM. COMPOS., 31:16111619, 2010. (C) 2009 Society of Plastics Engineers