α-Phase poly(vinylidene fluoride) (PVDF) has chains of zero dipole moments and is, therefore, nonpiezoelectric, while β-phase PVDF has the most significant piezoelectric properties among the polymorphs due to its polar chains. Although many reports describe PVDF as a suitable biomaterial due to its stability and biocompatibility, few considered the specific effects that the different polymorphs exert on cellular behaviour. We hypothesized that α- and β-phase PVDF will exert direct but different influences on cell attachment and metabolic activity. PVDF films were fabricated using N,N-dimethylformamide (DMF) and hexamethylphosphoramide (HMPA) by solvent casting. Samples were characterized by differential scanning calorimetry, Fourier transform infrared spectroscopy and X-ray diffraction. Films containing 83.5% α-phase PVDF (DMF-PVDFα) and 91.4% of β-phase PVDF (HMPA-PVDFβ within the crystalline regions were produced and used to evaluate in vitro attachment and metabolic activity of L929 cells. Cell metabolic activity on both PVDF conformations increased 3-fold over the 1-week culture period, with higher cell metabolic activity observed on DMF-PVDFα on day 5 of culture, compared to HMPA-PVDFβ. Cells grown on DMF-PVDFα were well-spread, flat and expressed spotted paxillin in focal adhesions that were mainly localized to perinuclear regions of the cells, while a high proportion of cells on HMPA-PVDFβ were bulging, round and expressed relatively fewer paxillin spots. Our results suggest that α-phase PVDF supports higher cell metabolic activity and better cell spreading compared to β-phase PVDF. Such variations can potentially be exploited for different biomedical applications.

This article investigates the effects of solvent polarity and salt addition on β‐phase poly(vinylidene fluoride) (PVDF) formation. Films were solvent cast in aprotic solvents of varying polarities with or without salt addition. Characterization was done by Fourier transformed infra‐red spectroscopy, differential scanning calorimetry, and scanning electron microscopy. Decreasing fractions of β‐phase PVDF was observed with increasing drying temperature when less polar solvents were used. The most polar solvent (hexamethylphosphoramide) consistently produced films with at least 90.0% β‐phase PVDF within the crystalline regions. Melting temperatures increased in correlation to absolute proportions of β‐phase PVDF. Salt addition increased the formation of β‐phase PVDF by 30%, with salts of higher valencies and smaller ionic radii resulting in more significant increases. Taken collectively, using solvents of higher polarities and addition of salts with high cationic valencies and small ionic radii will maximize β‐phase formation in solvent cast PVDF films. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

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A vast majority of people today spend more time indoors than outdoors. However, the air quality indoors may be as bad as or even worse than the air quality outside. This is due to the continuous circulation of the same air without proper ventilation and filtration systems, causing a buildup of pollutants. As such, indoor air quality monitoring should be considered more seriously. Indoor air quality (IAQ) is a measure of the air quality within and around buildings and relates to the health and comfort of building occupants. To determine the IAQ, computer modeling is done to simulate the air flow and human exposure to the pollutant. Currently, very few instruments are available to measure the indoor air pollution index. In this paper, we will review the list of techniques available for measuring IAQ, but our emphasis will be on indoor air toxicity monitoring.