Investigation of polymer phase behavior at heterogeneous polymer-polymer interfaces using secondary ion mass spectrometry

Changes in the thermodynamic behavior of polymer blends from bulk to heterogeneous interfaces is investigated using secondary ion mass spectrometry (SIMS). The use of a magnetic sector spectrometer (CAMECA IMS-6f) is fully explored in order to determine the optimal conditions in which to probe polymer surfaces and heterogeneous interfaces using three bilayer film systems, namely polystyrene (PS) with poly(methyl methacrylate) (PMMA), poly(cyclohexyl methacrylate) (PCHMA) with PMMA, and PS with poly(2-vinylpyridine) (P2VP). Two primary ion beams have been employed, O2+ with detection of positive secondary ions, and Cs+ with detection of negative secondary ions. It was found that each polymer thin film system must be closely investigated in order to determine the optimal conditions for depth profiling using SIMS. Three types of systems were further investigated using SIMS.; PCHMA and PS are miscible with each other, but each is highly immiscible with PMMA. Identifiable by the asymmetries in the binary mean-field interaction parameters chi, PS preferentially segregates to the PCHMA/PMMA interface. Secondary ion mass spectrometry was used to provide real-space depth profiles of dPS in a miscible blend with PCHMA. The initial dPS concentration was varied from 5-20% (v/v), and the blend film was annealed at 150°C on a film of PMMA for 42 h. X-ray reflectometry was used to determine the interfacial width between PCHMA and PMMA at 150°C. Using self-consistent mean-field theory, good agreement was found between the experimental and theoretical interfacial excess Z* of dPS at each concentration.; Isotopic labeling (deuteration) is known to affect the phase behavior of PS and PMMA blends, but little is known regarding the changes in the interfacial properties at the PS/PMMA interface due to deuteration of PS and/or PMMA. To investigate these potential changes, secondary ion mass spectrometry (SIMS) was used to measure real-space depth profiles of dPS in hPS:dPS/hPMMA bilayers, with the hPS:dPS blend being well within the single-phase region of the phase diagram. Profound changes in the thermodynamic behavior of this system at the polymer/polymer interface are observed in the form of significant segregation of dPS to the hPS:dPS/hPMMA interface. The observation of a depletion hole during the formation of an equilibrium excess of dPS implies that the energetic gain at the interface per dPS chain has to be > kT. (Abstract shortened by UMI.)...