ABSTRACT
Nanoscale self-assembly of block copolymer thin films has garnered significant research interest for nanotemplate design and membrane applications. To fulfill these roles, control of thin film morphology and orientation is critical. Solvent vapor annealing (SVA) treatments can be used to kinetically trap morphologies in thin films not achievable by traditional thermal treatments, but many variables affect the outcome of SVA, including solvent choice, total solvent concentration/swollen film thickness, and solvent removal rate. In this work, we systematically examined the effect of solvent removal rate on the final thin film morphology of a cylinder-forming ABA triblock copolymer. By kinetically trapping the film morphologies at key points during the solvent removal process and then using successive ultraviolet ozone (UVO) etching steps followed by atomic force microscopy (AFM) imaging to examine the through-film morphologies of the films, we determined that the mechanism for cylinder reorientation from substrate-parallel to substrate-perpendicular involved the propagation of changes at the free surface through the film toward the substrate as a front. The degree of reorientation increased with successively slower solvent removal rates. Furthermore, the AFM/UVO etching scheme permitted facile real-space analysis of the thin film internal structure in comparison to cross-sectional transmission electron microscopy.
Subject(s)
Crystallization/methods , Nanostructures/chemistry , Nanostructures/ultrastructure , Nanotechnology/methods , Polymers/chemistry , Equipment Design , Equipment Failure Analysis , Gases/chemistry , Gases/isolation & purification , Hardness , Hot Temperature , Macromolecular Substances/chemistry , Materials Testing , Molecular Conformation , Particle Size , Solvents/chemistry , Solvents/isolation & purification , Surface PropertiesABSTRACT
OBJECTIVE: The relationship between stress reactivity and total or central adiposity in children has not been widely studied. Data from two studies were combined to determine the relationship between reactivity to interpersonal stress and the adiposity of children. RESEARCH METHODS AND PROCEDURES: Stress reactivity to an interpersonal stressor (speech) was measured in 36 boys (9.8 +/- 1.3 years of age) and 27 girls (9.3 +/- 1.3 years of age). Total adiposity (percentage body fat) was estimated from skinfolds and central adiposity from the abdominal girth. Multiple regression was used to establish the associations of change in perceived stress and heart rate reactivity with adiposity. Age, sex, ethnicity, and baseline perceived stress and heart rate served as covariates for total adiposity. Fat mass was included as an additional covariate for the prediction of log abdominal girth (central adiposity). RESULTS: Based on adjusted beta-weights, change in perceived stress (beta = 1.13, p Subject(s)
Adipose Tissue/metabolism
, Stress, Psychological
, Body Composition
, Body Mass Index
, Cardiovascular Diseases/prevention & control
, Child
, Family Health
, Female
, Humans
, Male
, Perception
, Regression Analysis
, Sex Factors
, Social Class
