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1.
Environ Justice ; 17(1): 15-30, 2024 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-38660331

RESUMO

Background: Tree canopy cover has mental and physical health benefits for children, yet distributional environmental injustices in tree canopy cover near schools are rarely investigated. Some evidence suggests that tree canopy coverage positively influences aggregated school-level children's academic proficiency metrics. There is a lack of research if canopy cover moderates the negative effect of particulate matter on academic proficiency. Methods: We linked data on schools from the National Center for Education Statistics, Utah's Student Assessment of Growth and Excellence, the National Land Cover Database, and the U.S. Environmental Protection Agency. We used generalized estimating equations, which account for non-normally distributed data and clustering, to analyze data from the 2015 to 2016 school year. Results: Greater school social disadvantage (higher percentages of students qualifying for free/reduced price meals and higher percentages of racial/ethnic minority students) was significantly associated with reductions in tree canopy cover within 1000 m and 500 m of the school. Greater tree canopy coverage at 1000 m and 500 m was significantly associated with a lower percentage of students testing below proficient on year-end math and language arts exams. Additional days of peak fine particulate matter were associated with higher percentages of students testing below proficient in math. Discussion: Socially disadvantaged primary schools in Utah were surrounded by less canopy cover. There was a protective effect of tree canopy cover on academic proficiency in math and language arts. Conclusion: Findings suggest targeting carefully designed tree planting efforts at socially disadvantaged schools and testing interventions involving tree planting and changes in academic proficiency.

2.
Artigo em Inglês | MEDLINE | ID: mdl-38388655

RESUMO

BACKGROUND: Research demonstrates that chronic exposure to fine particulates (PM2.5) increases risks of neurodevelopmental conditions, such as intellectual disability (ID). Few studies have examined neurodevelopmental health impacts of pollution spikes exceeding 24-h (24-h) PM2.5 guidelines, despite relevance to the regulatory landscape. The current potential for regulatory changes to 24-h PM2.5 standards in the United States makes research on exceedances relevant. OBJECTIVE: To examine associations between 24-h PM2.5 exceedances and the risk of ID. METHODS: We conducted a retrospective case-control study of a sample of children in Utah, USA. We used generalized estimating equations to predict odds of ID based on the number of 24-h PM2.5 exceedance days during the preconception period and three trimesters of pregnancy. Exceedance days are defined as per current World Health Organization (WHO) [≥15 µg/m3] and current US Environmental Protection Agency (EPA) [≥35 µg/m3] 24-h guidelines. RESULTS: PM2.5 exceedances are associated with ID risk during the preconception and first trimester periods and not the second and third trimesters. During the preconception period, each day exceeding 15 µg/m3 or 35 µg/m3 was associated with a 1.023 (CI: 1.011-1.040) or 1.042 (CI: 1.026-1.059, p < 0.001) increase in odds of ID, respectively. During the first trimester, each day exceeding 15 µg/m3 or 35 µg/m3 was associated with a 1.032 (CI: 1.017-1.047) or 1.059 (CI: 1.030-1.088) increase in odds of ID, respectively. IMPACT STATEMENT: Potential regulatory movement on the US 24-h PM2.5 standard makes research that explicitly studies exceedances highly relevant. Yet few studies examine health effects of exceeding 24-h guidelines for any air pollutants. This study fills important gaps in the literature by examining associations between odds of intellectual disability and the count of days exceeding current 24-h PM2.5 guidelines, as established by the World Health Organization and US Environmental Protection Agency, during the prenatal period. We find that exceedances of both sets of guidelines, during the preconception and first trimester periods, are associated with ID risk.

3.
CBE Life Sci Educ ; 22(4): ar39, 2023 12.
Artigo em Inglês | MEDLINE | ID: mdl-37751501

RESUMO

Hispanic/Latinx young adults remain significantly underrepresented in science, technology, engineering, and mathematics (STEM) fields, yet the role families play in these young adults' trajectories in STEM is still underexamined. The purpose of this study was to examine the relational supports and constraints that Hispanic/Latinx college students in STEM majors experienced with their parents as they moved through college and transitioned into their first year of graduate school or full-time employment. Two rounds of interviews were conducted with 18 Hispanic/Latinx young adults who were part of an undergraduate STEM program at a Hispanic-majority university. Most of the study participants reported benefiting from immense emotional support from their parents; however, this emotional support was often simultaneously coupled with home-school value conflicts and a dynamic we call "conversational constraints." Results from this study point to important interventions involving family that might improve the rates of participation of Hispanic/Latinx students from a range of socioeconomic backgrounds in STEM fields.


Assuntos
Engenharia , Estudantes , Humanos , Adulto Jovem , Estudantes/psicologia , Engenharia/educação , Tecnologia/educação , Hispânico ou Latino , Matemática
4.
Ann N Y Acad Sci ; 1526(1): 8-15, 2023 08.
Artigo em Inglês | MEDLINE | ID: mdl-37391186

RESUMO

Having a diverse workforce in STEMM (science, technology, engineering, mathematics, and medicine) fields is essential for the United States to remain competitive in the global economy and to create a more just society. Faculty-mentored undergraduate research experiences have been identified as a high-impact practice for encouraging students from diverse backgrounds to pursue STEMM education and careers. Despite extensive research examining factors influencing the effectiveness of mentor-mentee relationships, there is still limited understanding of how differences or similarities in the social identities of mentors and mentees, which we term mentor-mentee discordance, impact undergraduates' research experiences and outcomes. In this perspective, we propose that mentor-mentee discordance should be conceptualized as a multidimensional, continuous construct and suggest a global index to measure varying degrees of discordance in mentoring relationships. We also offer a conceptual model that incorporates the Discordance Index to systematize the understanding of the effects of discordant mentoring relationships on student development across social contexts and over time. Finally, we provide recommendations for future researchers, STEMM educators, and program directors who are interested in using the Discordance Index.


Assuntos
Tutoria , Mentores , Humanos , Estados Unidos , Avaliação de Programas e Projetos de Saúde , Estudantes , Docentes
5.
CBE Life Sci Educ ; 22(3): ar32, 2023 09.
Artigo em Inglês | MEDLINE | ID: mdl-37347814

RESUMO

COVID-19 created unprecedented challenges for college students, highlighting the need to provide educational contexts that foster well-being. Summer undergraduate research experiences (SUREs) constitute a high-impact practice, yet little systematic knowledge exists about how the first surge of COVID-19 influenced undergraduate researchers' well-being. This knowledge is important for preparing for future disruptions. This study applies the student well-being model (SWBM) to examine how SURE status (e.g., modification vs. cancellation) impacted students' mental health and graduate school intentions using primary survey data collected from U.S. undergraduate researchers in science, technology, engineering, and mathematics (STEM) fields in Summer 2020 (n = 408, from 131 institutions). Just under half had their SURE canceled, and the others engaged in modified SUREs. Students whose SUREs were canceled had reduced anxiety severity (p < 0.05), but greater concerns about graduate school matriculation (p < 0.001), compared with students with modified SUREs. Results suggest that modified SUREs are a reasonable path forward under conditions where in-person contact is untenable. Results point toward potential improvements in higher education practices that may enhance student well-being following disruptive events. Program directors can address potential causes of anxiety in modified SUREs, advocate for student-centered adjustments to graduate admission processes, and use experiences during COVID-19 as a springboard to broaden participation in undergraduate research.


Assuntos
COVID-19 , Estudantes , Humanos , Intenção , Instituições Acadêmicas , Ansiedade
6.
Agric Human Values ; 40(1): 101-112, 2023.
Artigo em Inglês | MEDLINE | ID: mdl-35891801

RESUMO

In the 1930s, the Home Owners' Loan Corporation (HOLC) graded the mortgage security of urban US neighborhoods. In doing so, the HOLC engaged in the practice, imbued with racism and xenophobia, of "redlining" neighborhoods deemed "hazardous" for lenders. Redlining has caused persistent social, political and economic problems for communities of color. Linkages between redlining and contemporary food access remain unexamined, even though food access is essential to well-being. To investigate this, we used a census tract-level measure of low-income and low grocery store food access from the US Department of Agriculture Food Access Research Atlas, redlining data from Mapping Inequality Project, and demographic data from the American Community Survey. We employed generalized estimating equations with robust covariance estimates to analyze data pertaining to 10,459 census tracts in 202 US cities. Tracts that the HOLC graded as "C" ("decline in desirability") and "D" ("hazardous") had reduced contemporary food access compared to those graded "A" ("best"). Increases in contemporary census tract proportions of Black, Hispanic, or other racial/ethnic minority residents, as well as disabled residents, were associated with reduced food access. Increases in contemporary proportions of residents age 75 years and older or those without a car were associated with better food access. Tracts that underwent housing redevelopment since being graded had better food access, while those undergoing gentrification had reduced food access. Results suggest that issues of redlining, housing discrimination, racism, ableism, displacement, and food inaccessibility are deeply intertwined.

7.
Disabil Health J ; 16(2): 101403, 2023 04.
Artigo em Inglês | MEDLINE | ID: mdl-36473824

RESUMO

BACKGROUND: While natural disasters have been found to affect both disabled and subsidized rental housing residents negatively and disproportionately, previous studies have not examined if adverse disaster impacts experienced by disabled individuals in subsidized housing developments differ from those living in other housing. OBJECTIVE: We focused on Winter Storm Uri in Texas, USA, which lasted from February 10-20, 2021. We sought to: (1) compare differences in adverse impacts suffered by households with and without disabled persons; and (2) examine how residency in US Department of Housing and Urban Development (HUD)-assisted rental housing influences the severity of impacts for households with disabled persons. METHODS: We collected data from 790 randomly selected households in eight Texas metropolitan areas through a bilingual phone survey. Bivariate and multivariable statistical methods were utilized to compare adverse impacts suffered by households, based on both disability status and HUD-assisted housing residency. RESULTS: Households with disabled persons were more severely impacted by Uri than households without disabled persons, in terms of service disruptions, colder temperatures, slower recovery, and adverse experiences that have important health implications. Households with disabled persons residing in HUD-assisted housing were more negatively impacted and suffered more adverse experiences than those living in other housing. CONCLUSIONS: Residency in federally-assisted rental housing can worsen severity of adverse impacts and amplify disaster vulnerability for disabled individuals. These disparities based on disability and subsidized housing status emphasize the need for additional research to understand the impacts of disasters on disabled residents and formulate interventions that provide equitable protections.


Assuntos
Pessoas com Deficiência , Desastres , Humanos , Habitação , Habitação Popular , Texas
8.
Environ Res ; 218: 115009, 2023 02 01.
Artigo em Inglês | MEDLINE | ID: mdl-36495968

RESUMO

Prenatal fine particulate matter (PM2.5) exposure is an understudied risk factor for neurodevelopmental outcomes, including intellectual disability (ID). Associations among prenatal exposures and neurodevelopmental outcomes may vary depending on the timing of exposure. Limited numbers of studies examining PM2.5 and neurodevelopmental outcomes have considered exposures occurring during the preconception period. To address these gaps, we conducted a case-control study of children born in Utah between 2002 and 2008 (n = 1032). Cases were identified using methods developed by the Centers for Disease Control and Prevention's Autism and Developmental Disabilities Monitoring Network and matched with controls on birth year, sex, and birth county. We estimated the daily average PM2.5 concentration during a period spanning 12 weeks before the estimated conception date, as well as during each of the three trimesters at the maternal residential address listed on the child's birth certificate. In a multivariable model, the third (OR: 2.119, CI: 1.123-3.998, p = .021) and fourth (OR: 2.631, CI: 1.750-3.956, p < .001) quartiles for preconception average PM2.5 demonstrated significantly increased risk of ID relative to the first quartile. Second quartile preconception exposure was also associated with increased risk, though it did not reach significance (OR: 1.385, CI: 0.979-1.959, p = .07). The fourth quartile of first trimester average PM2.5 was positive and significant (OR: 2.278, CI: 1.522-3.411, p < .001); the third quartile was positive, but not significant (OR: 1.159, CI: 0.870-1.544, p = .312). Quartiles of second and third trimester were not associated with higher risk of ID. These findings from Utah, which were robust to a variety of sensitivity analyses, provide initial evidence that preconception and prenatal PM2.5 exposure may be associated with ID. Future studies are needed across other geographic locations and populations.


Assuntos
Poluentes Atmosféricos , Poluição do Ar , Deficiência Intelectual , Gravidez , Criança , Feminino , Humanos , Estudos de Casos e Controles , Deficiência Intelectual/induzido quimicamente , Deficiência Intelectual/epidemiologia , Utah/epidemiologia , Exposição Materna/efeitos adversos , Material Particulado/toxicidade , Material Particulado/análise , Poluentes Atmosféricos/toxicidade , Poluentes Atmosféricos/análise , Poluição do Ar/efeitos adversos , Poluição do Ar/análise
9.
Am J Public Health ; 113(1): 30-34, 2023 01.
Artigo em Inglês | MEDLINE | ID: mdl-36356281

RESUMO

We assessed sociodemographic disparities in basic service disruptions caused by Winter Storm Uri in Texas. We collected data through a bilingual telephone survey conducted in July 2021 (n = 753). Being Black, having children, and renting one's residence were associated with longer power outage durations; being Black was also associated with longer water outages. Our findings highlight the need to plan for and ameliorate inequitable service outages and their attendant health risks in climate change-related extreme weather events such as Uri. (Am J Public Health. 2023;113(1):30-34. https://doi.org/10.2105/AJPH.2022.307110).


Assuntos
Habitação , Água , Criança , Humanos , Texas/epidemiologia
10.
Soc Sci Med ; 315: 115523, 2022 12.
Artigo em Inglês | MEDLINE | ID: mdl-36379161

RESUMO

Previous research on health effects of extreme weather has emphasized heat events even though cold-attributable mortality exceeds heat-attributable mortality worldwide. Little is known about the mental health effects of cold weather events, which often cascade to produce secondary impacts like power outages, leaving a knowledge gap in context of a changing climate. We address that gap by taking a novel "cascading disaster health inequities" approach to examine winter storm-associated post-traumatic stress (PTS) using survey data (n = 790) collected in eight Texas metro areas following Winter Storm Uri in 2021, which occurred against the backdrop of COVID-19. The incidence of storm-related PTS was 18%. Being Black (odds ratio [OR]: 6.6), Hispanic (OR: 3.5), or of another non-White race (OR: 4.2) was associated with greater odds of PTS compared to being White, which indicates substantial racial/ethnic inequities in mental health impacts (all p < 0.05). Having a disability also increased odds of PTS (OR: 4.4) (p < 0.05). Having piped water outages (OR: 1.9) and being highly impacted by COVID-19 (OR: 3.3) increased odds of PTS (both p < 0.05). When modelling how COVID-19 and outages cascaded, we compared householders to those with no outages and low COVID-19 impacts. PTS was more likely (p < 0.05) if householders had a water or power outage and high COVID-19 impacts (OR: 4.4) and if they had water and power outages and high COVID-19 impacts (OR: 7.7). Findings provide novel evidence of racial/ethnic inequities and cascading effects with regard to extreme cold events amid the COVID-19 pandemic.


Assuntos
COVID-19 , Desastres , Transtornos de Estresse Pós-Traumáticos , Humanos , COVID-19/epidemiologia , Tempo (Meteorologia) , Pandemias , Texas/epidemiologia , Iniquidades em Saúde , Transtornos de Estresse Pós-Traumáticos/epidemiologia , Água
11.
Environ Res ; 214(Pt 4): 114038, 2022 11.
Artigo em Inglês | MEDLINE | ID: mdl-35961542

RESUMO

We conducted a novel investigation of neighborhood-level racial/ethnic exposure disparities employing measures aligned with long-term and short-term PM2.5 air pollution benchmarks across metropolitan contexts of the contiguous United States, 2012-2016. We used multivariable generalized estimating equations (GEE) to quantify PM2.5 exposure disparities based on the census tract composition of people of color (POC) and POC groups (Hispanic/Latina/x/o, Black, Asian). We examined eight census tract-level measures of longer-to-shorter term exposures derived from data on modeled daily ambient PM2.5 concentrations. We found associations between increased POC composition and greater exposure to all PM2.5 measures, with associations strengthening across measures of longer-to-shorter term exposures. In a GEE with a negative binomial distribution, a standard deviation increase in POC composition predicted a 0.6% increase (incidence rate ratio (IRR): 1.006, 95% confidence interval (CI): 1.005-1.008) in the number of days PM2.5 concentrations were ≥5 µg/m3 (longest-term benchmark). In a GEE with an inverse Gaussian distribution, a standard deviation increase in POC composition predicted a 0.110 µg/m3 (1.0%) increase (B: 0.110, 95% CI: 0.076-0.143) in mean PM2.5 concentration. In GEEs with a negative binomial distribution, the effect of a standard deviation increase in POC composition on exposure strengthened to 2.6% (IRR:1.026, 95% CI:1.017-1.035), 3.4% (IRR:1.034, 95% CI:1.022-1.047), 4.2% (IRR:1.042, 95% CI:1.025-1.058), 16.2% (IRR:1.162, 95% CI:1.117-1.210), 22.7% (IRR:1.227, 95% CI:1.137-1.325) and 28.3% (IRR:1.283, 95% CI:1.144-1.439) with respect to the number of days PM2.5 concentrations were ≥10, 12, 15, 25, 35 and 55.5 µg/m3. POC group models indicated exposure disparities based on greater Hispanic/Latina/x/o, Asian, and Black composition. Evidence for stronger POC associations with shorter-term (higher concentration) PM2.5 exceedances suggests that reducing PM2.5 would attenuate racial/ethnic exposure disparities.


Assuntos
Poluentes Atmosféricos , Poluição do Ar , Poluentes Atmosféricos/análise , Poluição do Ar/análise , Exposição Ambiental/análise , Humanos , Material Particulado/análise , Grupos Raciais , Estados Unidos
13.
Sci Rep ; 12(1): 9887, 2022 06 14.
Artigo em Inglês | MEDLINE | ID: mdl-35701654

RESUMO

Fine particulate matter 2.5 microns or less in diameter (PM2.5) is widely recognized to be a major public health concern. While ethnic/racial minority and lower socioeconomic status individuals in the US experience higher PM2.5 exposure, previous research on social disparities in PM2.5 exposure has not examined residents of federally-assisted public housing developments (PHDs). Here we present the first national-scale analysis of the relationship between outdoor PM2.5 exposure and PHD residency in the US, as well as exposure disparities within the population of households residing in PHDs. We integrated data on average annual PM2.5 concentrations (2011-2015) with US Department of Housing and Urban Development data on PHDs (2015), and socio-demographic information from the 2011-2015 American Community Survey. Results from multivariable generalized estimating equations indicated that PHD locations, units, and residents are significantly overrepresented in neighborhoods with greater PM2.5 exposure, after accounting for clustering, urbanization, and other socio-demographic factors. Additionally, significantly higher percentages of Black, Hispanic, disabled, and extremely low-income households reside in PHDs with greater PM2.5 exposure. Findings represent an important starting point for future research and emphasize the urgent need to identify gaps in environmental, public health, and housing policies that contribute to disproportionate air pollution exposures among PHD residents.


Assuntos
Poluentes Atmosféricos , Poluição do Ar , Poluentes Atmosféricos/análise , Poluição do Ar/análise , Exposição Ambiental/análise , Habitação , Humanos , Material Particulado/análise , Habitação Popular
14.
Artigo em Inglês | MEDLINE | ID: mdl-35682120

RESUMO

Undergraduate research is a high-impact practice on college campuses. How the COVID-19 pandemic has affected undergraduate researchers' progress is poorly understood. We examine how demographics, academic characteristics, research disruptions and faculty mentorship are associated with four barriers to research progress. Data are drawn from a survey of over 1000 undergraduate student researchers across the US. We examine students who actively continued to conduct faculty-mentored research during mid-March/April 2020 (n = 485). Using generalized estimating equations that control clustering by institution, we found economic hardship, discomfort teleconferencing, lower quality mentors, sexual minority status and higher grade point averages were associated with motivation problems. Economic hardship, serious illness, Internet connection issues, a lack of face-to-face meetings and lower a frequency of mentor-mentee communication were associated with a time crunch with regard to conducting research. Discomfort teleconferencing, Internet connection issues, a lack of face-to-face meetings and decrease in research workload were associated with task uncertainty. Economic hardship, serious illness and being an engineering major were associated with lacking needed tools for the research. In sum, economic hardship was an important correlate of research barriers, as were communication challenges and sexual minority status. Results can inform practical actions by research program directors and faculty undergraduate research mentors.


Assuntos
COVID-19 , COVID-19/epidemiologia , Humanos , Mentores , Pandemias , Estudantes , Universidades
15.
Sci Total Environ ; 836: 155630, 2022 Aug 25.
Artigo em Inglês | MEDLINE | ID: mdl-35508240

RESUMO

While heavy metals exposure is associated with intellectual disability (ID), little is known about associations between industrial pollution and ID. The objective of this analysis is to assess associations between estimated perinatal industrial pollution exposures from the US Environmental Protection Agency's Risk Screening Environmental Indicators Microdata and children's ID risk. We conducted a case-control study of children born in Utah from 2000 to 2008 (n = 1679). Cases were identified through the Center for Disease Control's Autism and Developmental Disabilities Monitoring Network's Utah site and matched with controls based on birth year, sex, and birth county. We used multivariable generalized estimating equations to examine associations between estimated perinatal industrial pollution exposures and ID risk. The fourth quartile of industrial pollution exposure was associated with increased odds of ID relative to the first (Odds Ratio [OR]: 1.73, 95% Confidence Interval [CI]: 1.23-2.44) and second (OR: 1.67, CI: 1.19-2.35) quartiles. Similarly, the third quartile was associated with increased odds of ID relative to the first (OR: 1.47, CI: 1.06-2.03) and second (OR: 1.41, CI: 1.02-1.96) quartiles. Findings were robust to varied model specifications. Maternal residential exposures to industrial pollution were associated with increased ID prevalence in Utah. Since environmental correlates of ID are understudied, additional research is needed.


Assuntos
Transtorno Autístico , Deficiência Intelectual , Transtorno Autístico/epidemiologia , Estudos de Casos e Controles , Criança , Feminino , Humanos , Deficiência Intelectual/epidemiologia , Exposição Materna , Gravidez , Utah/epidemiologia
18.
Ann N Y Acad Sci ; 1508(1): 137-154, 2022 02.
Artigo em Inglês | MEDLINE | ID: mdl-34542173

RESUMO

There is emerging literature on the disruptive effects of the COVID-19 pandemic on college students, but little is known about the impacts on undergraduate researchers (UGRs). On the basis of survey data collected in Summer 2020, this paper examines how less competent mentorship and COVID-19-related difficulties shaped UGRs' graduate school intentions. Results suggest that the pandemic strengthened UGRs' graduate school intentions when UGRs experienced fewer COVID-19-related difficulties. The pandemic weakened URG's graduate school intentions when they had a less competent faculty mentor. Having a more competent postgraduate mentor had a positive effect on UGRs' graduate school intentions in response to the pandemic. Those findings indicate that higher quality postgraduate mentorship may serve as an effective surrogate for lower quality faculty mentorship. Findings suggest that immediate strategies are needed to bolster graduate school aspirations among specific groups of UGRs in response to the pandemic. UGRs of particular concern include those who were highly impacted by COVID-19 with less competent mentors, were first-generation college students, had less prior research experience, had their Summer 2020 research experiences canceled, and were social/behavioral sciences majors.


Assuntos
COVID-19/epidemiologia , Educação de Pós-Graduação , Intenção , Pesquisadores/psicologia , COVID-19/virologia , Humanos , Mentores , SARS-CoV-2/isolamento & purificação
19.
J Am Coll Health ; : 1-11, 2021 Dec 14.
Artigo em Inglês | MEDLINE | ID: mdl-34905697

RESUMO

OBJECTIVE: The objective was to examine mental health of undergraduate researchers (UGRs) during the COVID-19 pandemic. PARTICIPANTS: We surveyed 962 UGRs who were conducting research in Spring 2020 at over 100 US universities. METHODS: We conducted an online survey in July 2020. We analyzed data using descriptive statistics and multivariable generalized estimating equations. RESULTS: 63% reported at least mild anxiety and 73% reported at least mild depression based on GAD-7 and PHQ-9 scores; 15.2% reported severe anxiety (score ≥ 15) and 23.4% reported severe depression (score ≥ 15). More COVID-19-related adverse event experiences were associated with more severe anxiety and depression, as were first-generation status, woman gender, and LGBQ status. Greater social support was protective, and significantly more so for men (vs. women) and continuing generation (vs. first generation) students. CONCLUSION: Faculty have an important role in the mental health of their mentees. Additional interventions are needed to better support women and first-generation students.Supplemental data for this article can be accessed online at.

20.
Polymers (Basel) ; 13(23)2021 Dec 03.
Artigo em Inglês | MEDLINE | ID: mdl-34883741

RESUMO

We studied the kinetics of swelling in high-χ lamellar-forming poly(styrene)-block- poly(lactic acid) (PS-b-PLA) block copolymer (BCP) by varying the heating rate and monitoring the solvent vapour pressure and the substrate temperature in situ during solvo-thermal vapour annealing (STVA) in an oven, and analysing the resulting morphology. Our results demonstrate that there is not only a solvent vapour pressure threshold (120 kPa), but also that the rate of reaching this pressure threshold has a significant effect on the microphase separation and the resulting morphologies. To study the heating rate effect, identical films were annealed in a tetrahydrofuran (THF) vapour environment under three different ramp regimes, low (rT<1 °C/min), medium (24 °C/min), for 60, 90 and 120 min, respectively, while the solvent vapour pressure and the substrate temperature were measured in real time. The translational order improved significantly with increasing the heating rate. The solvent mass uptake calculated for the different ramp regimes during annealing is linearly proportional to time, indicating that the swelling kinetics followed Case II diffusion. Two stages of the swelling behaviour were observed: (i) diffusion at the initial stages of swelling and (ii) stress relaxation, controlled at later stages. Films with a faster rate of increase in vapour pressure (rP>2 kPa/min) reached the pressure threshold value at an early stage of the swelling and attained a good phase separation. According to our results, highly ordered patterns are only obtained when the volume fraction of the solvent exceeds the polymer volume fraction, i.e., (φs≥φp), during the swelling process, and below this threshold value (φs=0.5), the films did not obtain a good structural order, even at longer annealing times.

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