Phase Separation in Poly(tert-butyl acrylate)/Polyhedral Oligomeric Silsesquioxane (POSS) Thin Film Blends

Abstract

Phase separation in thin film blends of poly(tert-butyl acrylate) (PtBA) and a polyhedral oligomeric silsesquioxane (POSS), trisilanolphenyl-POSS (TPP), is studied as functions of annealing temperature and time, using reflected light optical microscopy, atomic force microscopy, and X-ray photoelectron spectroscopy. The results demonstrate that the PtBA/TPP blend system confined to thin films ( approximately 90 nm) exhibits lower critical solution temperature (LCST) behavior with a critical temperature of approximately 70 degrees C and a critical composition of 60 wt % PtBA with insignificant dewetting at the phase boundary. Off-critical spinodal behavior is observed for 58 and 62 wt % PtBA blend films. Phase separation by nucleation and growth is observed for all compositions outside the window between 58 and 62 wt % PtBA. The temporal evolution of spinodal decomposition in 60 wt % PtBA blend films is explored at annealing temperatures of 75, 85, 95, and 105 degrees C. The morphological evolution in 60 wt % PtBA blend films is similar for all experimental temperatures (75, 85, 95, and 105 degrees C) with the expected shorter time scales for phase evolution at higher annealing temperatures. Fast Fourier transforms of optical micrographs reveal that these blend films immediately undergo phase separation by spinodal decomposition during temperature jump experiments. Power law scaling for the characteristic wavevector with time (q approximately t(n) with n approximately -1/4 to -1/3) for domain growth during the early stages of phase separation yields to domain pinning at the later stages for 60 wt % PtBA blend films annealed at 75, 85, and 95 degrees C. In contrast, domain growth is pinned over the entire experimental time scale for 60 wt % PtBA blend films annealed at 105 degrees C.

Structure–property evaluation of trisilanolphenyl POSS®/polysulfone composites as a guide to POSS melt blending

“…While not a positive outcome in the sense of reinforcing polysulfone using this grade of POSS this system has brought to attention the importance of phase behavior when designing these melt blended POSS composites. Work from Esker and coworkers18, 19 shows that the phase behavior of these POSS systems can be determined experimentally and used to design systems with desired qualities. Also working towards this theme Morgan et al20 have shown that solubility parameters can be calculated for POSS‐polymer combinations which have a noted effect on the morphology of the final composite.…”

Nonlinear phase‐separation behavior of poly(methyl methacrylate)/poly(styrene‐co‐maleic anhydride) blends

“…Liquid–liquid phase‐separation behavior of polymer blends having lower critical solution temperature (LCST) has been investigated extensively over the past several decades . In particular, the mechanism and kinetics of different phase‐separation behaviors, such as nucleation and growth and spinodal decomposition (SD), were emphasized .…”

A Polymer Interfacial Modifier Synthesized by Living Anionic Polymerization: Incorporation of Inorganic Blocks to Chain Ends

“…The surface of PPMP films was homogeneously covered with a 1 nm layer of POSS blocks . If the POSS blocks are not connected to polymer chains, they can be easily self‐aggregated and crystallized, leading to a formation of the rough surface . Also, although PPMP can be prepared by other methods such as controlled radical polymerization, the molecular weight distribution of PPMP by the living anionic polymerization is the narrowest.…”