Critical analysis of self-doping and water-soluble n-type organic semiconductors: structures and mechanisms

Self-doping organic semiconductors provide a promising route to avoid instabilities and morphological issues associated with molecular n-type dopants. Structural characterization of a naphthalenetetracarboxylic diimide (NDI) semiconductor covalently bound to an ammonium hydroxide group is presented. The dopant precursor was found to be the product of an unexpected base catalyzed hydrolysis, which was reversible. The reversible hydrolysis had profound consequences on the chemical composition, morphology, and electronic performance of the doped films. In addition, we investigated the degradation mechanism of the quaternary ammonium group and the subsequent doping of NDI. These findings reveal that the products of more than one chemical reaction during processing of films must be considered when utilizing this promising class of water-soluble semiconductors

Tracing river chemistry in space and time : dissolved inorganic constituents of the Fraser River, Canada

Author Posting. © The Author(s), 2013. This is the author's version of the work. It is posted here by permission of Elsevier for personal use, not for redistribution. The definitive version was published in Geochimica et Cosmochimica Acta 124 (2014): 283-308, doi:10.1016/j.gca.2013.09.006.The Fraser River basin in southwestern Canada bears unique geologic and climatic features which make it an ideal setting for investigating the origins, transformations and delivery to the coast of dissolved riverine loads under relatively pristine conditions. We present results from sampling campaigns over three years which demonstrate the lithologic and hydrologic controls on fluxes and isotope compositions of major dissolved inorganic runoff constituents (dissolved nutrients, major and trace elements, 87Sr/86Sr, δD). A time series record near the Fraser mouth allows us to generate new estimates of discharge-weighted concentrations and fluxes, and an overall chemical weathering rate of 32 t km-2 y-1. The seasonal variations in dissolved inorganic species are driven by changes in hydrology, which vary in timing across the basin. The time series record of dissolved 87Sr/86Sr is of particular interest, as a consistent shift between higher (“more radiogenic”) values during spring and summer and less radiogenic values in fall and winter demonstrates the seasonal variability in source contributions throughout the basin. This seasonal shift is also quite large (0.709 – 0.714), with a discharge-weighted annual average of 0.7120 (2 s.d. = 0.0003). We present a mixing model which predicts the seasonal evolution of dissolved 87Sr/86Sr based on tributary compositions and water discharge. This model highlights the importance of chemical weathering fluxes from the old sedimentary bedrock of headwater drainage regions, despite their relatively small contribution to the total water flux.This work was supported by the WHOI Academic Programs Office and MIT PAOC Houghton Fund to BMV, a WHOI Arctic Research Initiative grant to ZAW, NSF-ETBC grant OCE-0851015 to BPE and TIE, and NSF grant EAR-1226818 to BPE

Influence of Side Chain Interdigitation On Strain and Charge Mobility of Planar Indacenodithiophene Copolymers

Indacenodithiophene (IDT) copolymers are a class of conjugated polymers that have limited long-range order and high hole mobilities, which makes them promising candidates for use in deformable electronic devices. Key to their high hole mobilities is the coplanar monomer repeat units within the backbone. Poly(indacenodithiophene-benzothiadiazole) (PIDTC16-BT) and poly(indacenodithiophene-thiapyrollodione) (PIDTC16-TPDC1) are two IDT copolymers with planar backbones, but they are brittle at low molecular weight and have unsuitably high elastic moduli. Substitution of the hexadecane (C16) side chains of the IDT monomer with isocane (C20) side chains was performed to generate a new BT-containing IDT copolymer: PIDTC20-BT. Substitution of the methyl (C1) side chain on the TPD monomer for an octyl (C8) and 6-ethylundecane (C13B) afford two new TPD-containing IDT copolymers named PIDTC16-TPDC8 and PIDTC16-TPDC13B, respectively. Both PIDTC16-TPDC8 and PIDTC16-TPDC13B are relatively well deformable, have a low yield strain, and display significantly reduced elastic moduli. These mechanical properties manifest themselves because the lengthened side chains extending from the TPD-monomer inhibit precise intermolecular ordering. In PIDTC16-BT, PIDTC20-BT and PIDTC16-TPDC1 side chain ordering can occur because the side chains are only present on the IDT subunit, but this results in brittle thin films. In contrast, PIDTC16-TPDC8 and PIDTC16-TPDC13B have disordered side chains, which seems to lead to low hole mobilities. These results suggest that disrupting the interdigitation in IDT copolymers through comonomer side chain extension leads to more ductile thin films with lower elastic moduli, but decreased hole mobility because of altered local order in the respective thin films. Our work, thus, highlights the trade-off between molecular packing structure for deformable electronic materials and provides guidance for designing new conjugated polymers for stretchable electronics

An ordered, self-assembled nanocomposite with efficient electronic and ionic transport

Mixed conductors-materials that can efficiently conduct both ionic and electronic species-are an important class of functional solids. Here we demonstrate an organic nanocomposite that spontaneously forms when mixing an organic semiconductor with an ionic liquid and exhibits efficient room-temperature mixed conduction. We use a polymer known to form a semicrystalline microstructure to template ion intercalation into the side-chain domains of the crystallites, which leaves electronic transport pathways intact. Thus, the resulting material is ordered, exhibiting alternating layers of rigid semiconducting sheets and soft ion-conducting layers. This unique dual-network microstructure leads to a dynamic ionic/electronic nanocomposite with liquid-like ionic transport and highly mobile electronic charges. Using a combination of operando X-ray scattering and in situ spectroscopy, we confirm the ordered structure of the nanocomposite and uncover the mechanisms that give rise to efficient electron transport. These results provide fundamental insights into charge transport in organic semiconductors, as well as suggesting a pathway towards future improvements in these nanocomposites

An ordered, self-assembled nanocomposite with efficient electronic and ionic transport

Mixed conductors-materials that can efficiently conduct both ionic and electronic species-are an important class of functional solids. Here we demonstrate an organic nanocomposite that spontaneously forms when mixing an organic semiconductor with an ionic liquid and exhibits efficient room-temperature mixed conduction. We use a polymer known to form a semicrystalline microstructure to template ion intercalation into the side-chain domains of the crystallites, which leaves electronic transport pathways intact. Thus, the resulting material is ordered, exhibiting alternating layers of rigid semiconducting sheets and soft ion-conducting layers. This unique dual-network microstructure leads to a dynamic ionic/electronic nanocomposite with liquid-like ionic transport and highly mobile electronic charges. Using a combination of operando X-ray scattering and in situ spectroscopy, we confirm the ordered structure of the nanocomposite and uncover the mechanisms that give rise to efficient electron transport. These results provide fundamental insights into charge transport in organic semiconductors, as well as suggesting a pathway towards future improvements in these nanocomposites

Abstract MP03: The Association of the Parent-Child Acculturation Gap With Obesity and Cardiometabolic Risk in Hispanic/Latino Youth: Results From the Hispanic Community Children's Health Study/Study of Latino Youth (SOL Youth)

Introduction: Hispanic/Latino youth are disproportionately burdened by obesity and have a high prevalence of pre-diabetes and dyslipidemia. Acculturation may help explain this elevated cardiometabolic risk. Within immigrant families, parents and children acculturate at different rates. A difference in the degree of acculturation, known as the “acculturation gap”, between parents and their children has been associated with behaviors that may increase cardiometabolic risk in youth. However, no previous studies have investigated the association between the parent-child acculturation gap and cardiometabolic health. Hypothesis: We tested whether greater gaps in parent-child acculturation were associated with worse cardiometabolic health in Hispanic/Latino youth. Methods: Hispanic/Latino youth ( n =1466, 8-16-year-olds) and parents from the Hispanic Community Children’s Health Study/Study of Latino Youth (SOL Youth) were examined. Mean scores on the Brief Acculturation Rating Scale for Mexican Americans-II (ARSMA-II) Anglo and Latino Orientation Scales (AOS and LOS, respectively) were used to represent parent and youth acculturation. The Brief ARSMA-II primarily assesses language use patterns on a 5-point Likert-type scale, with higher scores on the AOS indicating a preference for English and higher scores on the LOS indicating a preference for Spanish. Cardiometabolic markers included youth body mass index (BMI) percentile, blood pressure percentiles, fasting glucose, HOMA-IR, HbA1c, cholesterol, triglycerides, and hsCRP. Missing data were addressed using multiple imputation. Survey-weighted multivariable linear regression examined associations of youth, parent, and youth x parent (the acculturation gap) scores for the AOS and LOS scales separately with each cardiometabolic marker. Results: On average, compared to their parents, youth reported a greater preference for English and a lower preference for Spanish (AOS=4.2 vs. 2.7; LOS=3.1 vs. 4.2, respectively). Greater discordance (i.e., an acculturation gap) in parent and youth AOS scores was associated with elevated BMI percentile only (p-for-interaction≤0.001). The LOS acculturation gap was not associated with any cardiometabolic measures. Adjustment for acculturative stress, family functioning and closeness, parenting style, and youth’s diet and physical activity did not alter the findings. Removal of non-significant acculturation gaps indicated an inverse association between parent AOS score and youth SBP percentile (β=-2.47, 95% CI: -4.73, -0.21) and between parent LOS score and youth total cholesterol (β=-2.87, 95% CI: -5.52, -0.21). Conclusions: Discrepancies in English language use in parent-child dyads may relate to increased obesity risk in Hispanic/Latino youth. Future studies are needed to identify mediators of this association, such as general stress and English language fluency

The Association of the Parent-Child Language Acculturation Gap with Obesity and Cardiometabolic Risk in Hispanic/Latino Youth: Results from the Hispanic Community Children's Health Study/Study of Latino Youth (SOL Youth)

Hispanic/Latino youth are disproportionately burdened by obesity and have a high prevalence of prediabetes and dyslipidemia. Differences in parent and child acculturation related to language use and preference (i.e., language acculturation) are associated with adverse cardiometabolic health behaviors, but no study has examined associations with cardiometabolic markers. To determine whether discordance in parent-child language acculturation (parent-child acculturation gap) was associated with poor youth cardiometabolic health. Hispanic/Latino 8-16-year-olds (n = 1,466) and parents from the Hispanic Community Children's Health Study/Study of Latino Youth (SOL Youth) were examined. Mean scores for the Brief ARSMA-II's Anglo (AOS) and Latino (LOS) Orientation Scales represented language acculturation. Cardiometabolic markers included youth body mass index (BMI) percentile, blood pressure percentiles, and dysglycemia and hyperlipidemia measures. Missing data were imputed. Survey-weighted multivariable linear regression examined the association of youth, parent, and youth × parent (the acculturation gap) AOS and LOS scores separately with each cardiometabolic marker. Youth reported greater English and lower Spanish use than parents. Greater discordance in AOS scores was associated with elevated BMI percentile only (p-for-interaction < .01). The LOS acculturation gap was not associated with any outcome. Adjustment for acculturative stress, family functioning and closeness, parenting style, and youth's diet and physical activity did not alter findings. Removal of nonsignificant acculturation gaps did not indicate an association between individual youth or parent AOS or LOS scores and any cardiometabolic marker. Discordance in Hispanic/Latino parent-child dyads' English use may relate to increased risk for childhood obesity. Future studies should identify mediators of this association

Role of aggregates and microstructure of mixed-ionic-electronic-conductors on charge transport in electrochemical transistors

Synthetic efforts have delivered a library of organic mixed ionic-electronic conductors (OMIECs) with high performance in electrochemical transistors. The most promising materials are redox-active conjugated polymers with hydrophilic side chains that reach high transconductances in aqueous electrolytes due to volumetric electrochemical charging. Current approaches to improve transconductance and device stability focus mostly on materials chemistry including backbone and side chain design. However, other parameters such as the initial microstructure and microstructural rearrangements during electrochemical charging are equally important and are influenced by backbone and side chain chemistry. In this study, we employ a polymer system to investigate the fundamental electrochemical charging mechanisms of OMIECs. We couple in situ electronic charge transport measurements and spectroelectrochemistry with ex situ X-ray scattering electrochemical charging experiments and find that polymer chains planarize during electrochemical charging. Our work shows that the most effective conductivity modulation is related to electrochemical accessibility of well-ordered, interconnected aggregates that host high mobility electronic charge carriers. Electrochemical stress cycling induces microstructural changes, but we find that these aggregates can largely maintain order, providing insights on the structural stability and reversibility of electrochemical charging in these systems. This work shows the importance of material design for creating OMIECs that undergo structural rearrangements to accommodate ions and electronic charge carriers during which percolating networks are formed for efficient electronic charge transport