Synthesis of Monodisperse, Highly Cross-Linked, Fluorescent PMMA Particles by Dispersion Polymerization

We describe a facile method to synthesize sterically stabilized monodisperse fluorescent poly(methyl methacrylate) (PMMA) colloids in the polar solvent mixture water/methanol with either a core-shell or a homogeneously cross-linked structure by dispersion polymerization. The particles were sterically stabilized by the polymer poly(vinylpyrrolidone) (PVP). The morphology of the particles was controlled by varying the moment at which the gradual addition of cross-linker and dye was started. The absence of these extra agents at a time when the particle nuclei formed reduced the negative effects on this important process to a minimum and produced a core-shell structure, whereas an essentially homogeneously cross-linked fluorescent polymer colloid structure could be obtained by reducing the starting time of the addition of dye and cross-linker to zero. Three different dyes were chemically incorporated into the polymer network. Such dyes are important for the use of the particles in confocal scanning laser microscopy studies aimed at characterizing concentrated dispersions quantitatively in real space. A series of PMMA particles with different sizes were obtained through the variation of the weight ratio of solvents and the content of cross-linker. Furthermore, the swelling properties of the cross-linked PMMA particles in a good solvent (tetrahydrofuran) were investigated. The particles were stable in polar solvents (water and formamide) but could also successfully be transferred to apolar solvents such as decahydronaphthalene (decalin). The PVP stabilizer also allowed the particles to be permanently bonded in flexible strings by the application of an external electric field

The Predictive Syndemic Effect of Multiple Psychosocial Problems on Health Care Costs and Utilization among Sexual Minority Women

Previous studies documenting sexual minority women’s disproportionate risk for a range of medical, mental health, and substance use disorders have not provided a predictive framework for understanding their interrelations and outcomes. The present study aimed to address this gap by testing the syndemic effect of co-occurring psychosocial problems on 7-year health care costs and utilization among sexual minority women. The sample was comprised of sexual minority women (N = 341) who were seen at an urban LGBT-affirmative community health center. Medical and mental health care utilization and cost data were extracted from electronic medical records. Demographically adjusted regression models revealed that co-occurring psychosocial problems (i.e., childhood sexual abuse, partner violence, substance use, and mental health distress [history of suicide attempt]) were all strongly interrelated. The presence of these indicators had a syndemic (additive) effect on medical costs and utilization and mental health utilization over 7-year follow-up, but no effect on 7-year mental health costs. These results suggest that the presence and additive effect of these syndemic conditions may, in part, explain increased medical costs and utilization (and higher medical morbidity) among sexual minority women