ABSTRACT
Ion conducting block copolymers can overcome traditional limitations of homopolymer electrolytes by phase separating into nanoarchitectures that can be simultaneously optimized for two or more orthogonal material properties such as high ionic conductivity and mechanical stability. A key challenge in understanding the ion transport properties of these materials is the difficulty of extracting structure-function relationships without having complete knowledge of all nanoscale transport pathways in bulk samples. Here we demonstrate a method for deriving structure-transport relationships for ion conducting block copolymers using thin films and interdigitated electrodes. Well-defined and directly imaged structure in films of poly(styrene)-block-poly(2-vinylpyridine) is controlled using techniques of directed self-assembly then the poly(2-vinylpyridine) is selectively converted into an ion conductor. The ion conductivity is found to be directly proportional to the total number of connected paths between electrodes and the path length. A single defect such as a dislocation anywhere in the path of an ion conducting route disconnects and precludes that pathway from contributing to the conductivity and results in an increase in the dielectric parameter of the film. When all the ion conduction pathways are blocked between electrodes, the conductivity is negligible, 4 orders of magnitude lower compared to a completely connected morphology and the dielectric parameter increases by a factor of 50. These results have profound implications for the interpretation, design, and processing of block copolymer electrolytes for applications as ion conducting membranes.
ABSTRACT
CONTEXT: Substance abuse and its related problems have become a serious public health issue, particularly in underserved border and rural communities. Conventional therapies have not always been effective. Literature regarding the use of auricular acupressure in substance abuse treatment is limited. OBJECTIVE: To examine the efficacy of auricular acupressure in addition to usual care in substance abuse treatment, which has been limited. DESIGN AND SETTING: This placebo-controlled pilot study was carried out in a community mental health center in a US-Mexico border city (Las Cruces) in southwestern New Mexico. PARTICIPANTS: A majority were Hispanic males with an average age of 32.8 years. Participants reported an average lifetime use of drug of choice of 14 years. INTERVENTION: In addition to usual care, participants received specific acupressure treatment and placebo acupressure treatment. The acupressure treatment was offered once a week for 6 consecutive weeks. MAIN OUTCOME MEASURES: The Hopkins Symptom Checklist (SCL-20) Depression Scale was administered before and after 6 weeks of treatment to assess changes in emotional distress. Brief Substance Craving Scale was used at baseline and weekly for 6 weeks to assess changes in craving. RESULTS: Both specific and placebo acupressure groups showed a significant reduction in craving at the end of treatment, with the specific acupressure group having a greater and more steady reduction in craving. Both specific acupressure and usual-care-only groups demonstrated a significant reduction in emotional stress. CONCLUSION: Overall, there was a positive response to the specific auricular acupressure treatment on psychological distress, craving, and drug/alcohol use measures. These encouraging preliminary results need to be duplicated in studies with larger sample sizes and longer treatment phases.
