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1.
J Dev Orig Health Dis ; 14(2): 175-181, 2023 04.
Article in English | MEDLINE | ID: mdl-36408681

ABSTRACT

High-quality evidence from prospective longitudinal studies in humans is essential to testing hypotheses related to the developmental origins of health and disease. In this paper, the authors draw upon their own experiences leading birth cohorts with longitudinal follow-up into adulthood to describe specific challenges and lessons learned. Challenges are substantial and grow over time. Long-term funding is essential for study operations and critical to retaining study staff, who develop relationships with participants and hold important institutional knowledge and technical skill sets. To maintain contact, we recommend that cohorts apply multiple strategies for tracking and obtain as much high-quality contact information as possible before the child's 18th birthday. To maximize engagement, we suggest that cohorts offer flexibility in visit timing, length, location, frequency, and type. Data collection may entail multiple modalities, even at a single collection timepoint, including measures that are self-reported, research-measured, and administrative with a mix of remote and in-person collection. Many topics highly relevant for adolescent and young adult health and well-being are considered to be private in nature, and their assessment requires sensitivity. To motivate ongoing participation, cohorts must work to understand participant barriers and motivators, share scientific findings, and provide appropriate compensation for participation. It is essential for cohorts to strive for broad representation including individuals from higher risk populations, not only among the participants but also the staff. Successful longitudinal follow-up of a study population ultimately requires flexibility, adaptability, appropriate incentives, and opportunities for feedback from participants.


Subject(s)
Birth Cohort , Adolescent , Child , Young Adult , Humans , Prospective Studies , Self Report
2.
J Pediatr ; 252: 40-47.e5, 2023 01.
Article in English | MEDLINE | ID: mdl-35987367

ABSTRACT

OBJECTIVE: To evaluate associations between changes in weight, length, and weight/length ratio during infancy and outcomes later in life among individuals born extremely preterm. STUDY DESIGN: Among participants in the Extremely Low Gestational Age Newborn (ELGAN) study, we measured weight and length at discharge from the neonatal intensive care unit (NICU) and at age 2 years and evaluated neurocognitive, psychiatric, and health outcomes at age 10 years and 15 years. Using multivariable logistic regression, we estimated associations between gains in weight, length, and weight/length ratio z-scores between discharge and 2 years and outcomes at 10 and 15 years. High gain was defined as the top quintile of change; low gain, as the bottom quintile of change. RESULTS: High gains in weight and weight/length were associated with greater odds of obesity at 10 years, but not at 15 years. These associations were found only for females. High gain in length z-score was associated with lower odds of obesity at 15 years. The only association found between high gains in growth measures and more favorable neurocognitive or psychiatric outcomes was between high gain in weight/length and lower odds of cognitive impairment at age 10 years. CONCLUSIONS: During the 2 years after NICU discharge, females born extremely preterm with high gains in weight/length or weight have greater odds of obesity at 10 years, but not at 15 years. Infants with high growth gains in the 2 years after NICU discharge have neurocognitive and psychiatric outcomes in middle childhood and adolescence similar to those of infants with lower gains in weight and weight/length.


Subject(s)
Infant, Extremely Premature , Premature Birth , Adolescent , Female , Infant, Newborn , Infant , Child , Humans , Child, Preschool , Intensive Care Units, Neonatal , Gestational Age , Obesity , Outcome Assessment, Health Care
3.
J Pediatr Nurs ; 66: 36-43, 2022.
Article in English | MEDLINE | ID: mdl-35623186

ABSTRACT

PURPOSE: The purpose of this qualitative descriptive study was to explore primary caregivers' perception of how social-environmental characteristics, and their own role as primary caregivers, affected their extremely preterm adolescent's well-being. METHODS: Participants were 20 mothers who identified as the primary caregiver of an adolescent born extremely prematurely (<28 weeks gestation) enrolled in the ELGAN cohort study. Data was collected through individual interviews and was analyzed using inductive content analysis. RESULTS: A total of three themes, and five subthemes, were identified. The two main themes were "familial impact to health and well-being," and "contributors and barriers at the community level." This study described specific familial and community contributors to child and caregiver well-being, including: the importance of advocacy, participating in community activities, and social and familial support networks. CONCLUSIONS: Overall, while there are individual level characteristics that contribute to well-being, a support structure at the family and community level is essential to children born extremely prematurely, and their mother's, well-being. PRACTICE IMPLICATIONS: Healthcare providers caring for these families should understand that not only are extremely preterm youth affected by prematurity, but caregivers are also deeply impacted. Therefore, it is essential that maternal and family care is emphasized by nurses and healthcare providers.


Subject(s)
Caregivers , Infant, Extremely Premature , Adolescent , Child , Cohort Studies , Female , Humans , Infant, Newborn , Mothers , Perception
4.
Radiology ; 304(2): 419-428, 2022 08.
Article in English | MEDLINE | ID: mdl-35471112

ABSTRACT

Background Extremely preterm (EP) birth is associated with higher risks of perinatal white matter (WM) injury, potentially causing abnormal neurologic and neurocognitive outcomes. MRI biomarkers distinguishing individuals with and without neurologic disorder guide research on EP birth antecedents, clinical correlates, and prognoses. Purpose To compare multiparametric quantitative MRI (qMRI) parameters of EP-born adolescents with autism spectrum disorder, cerebral palsy, epilepsy, or cognitive impairment (ie, atypically developing) with those without (ie, neurotypically developing), characterizing sex-stratified brain development. Materials and Methods This prospective multicenter study included individuals aged 14-16 years born EP (Extremely Low Gestational Age Newborns-Environmental Influences on Child Health Outcomes Study, or ELGAN-ECHO). Participants underwent 3.0-T MRI evaluation from 2017 to 2019. qMRI outcomes were compared for atypically versus neurotypically developing adolescents and for girls versus boys. Sex-stratified multiple regression models were used to examine associations between spatial entropy density (SEd) and T1, T2, and cerebrospinal fluid (CSF)-normalized proton density (nPD), and between CSF volume and T2. Interaction terms modeled differences in slopes between atypically versus neurotypically developing adolescents. Results A total of 368 adolescents were classified as 116 atypically (66 boys) and 252 neurotypically developing (125 boys) participants. Atypically versus neurotypically developing girls had lower nPD (mean, 557 10 × percent unit [pu] ± 46 [SD] vs 573 10 × pu ± 43; P = .04), while atypically versus neurotypically developing boys had longer T1 (814 msec ± 57 vs 789 msec ± 82; P = .01). Atypically developing girls versus boys had lower nPD and shorter T2 (eg, in WM, 557 10 × pu ± 46 vs 580 10 × pu ± 39 for nPD [P = .006] and 86 msec ± 3 vs 88 msec ± 4 for T2 [P = .003]). Atypically versus neurotypically developing boys had a more moderate negative association between T1 and SEd (slope, -32.0 msec per kB/cm3 [95% CI: -49.8, -14.2] vs -62.3 msec per kB/cm3 [95% CI: -79.7, -45.0]; P = .03). Conclusion Atypically developing participants showed sexual dimorphisms in the cerebrospinal fluid-normalized proton density (nPD) and T2 of both white matter (WM) and gray matter. Atypically versus neurotypically developing girls had lower WM nPD, while atypically versus neurotypically developing boys had longer WM T1 and more moderate T1 associations with microstructural organization in WM. © RSNA, 2022 Online supplemental material is available for this article.


Subject(s)
Autism Spectrum Disorder , Infant, Extremely Premature , Adolescent , Brain/diagnostic imaging , Child , Female , Humans , Infant, Newborn , Magnetic Resonance Imaging/methods , Male , Prospective Studies , Protons
5.
J Am Acad Child Adolesc Psychiatry ; 61(7): 892-904.e2, 2022 07.
Article in English | MEDLINE | ID: mdl-34973366

ABSTRACT

OBJECTIVE: To evaluate the prevalence, co-occurrence, sex differences, and functional correlates of DSM-5 psychiatric disorders in 15-year-old adolescents born extremely preterm. METHOD: The Extremely Low Gestational Age Newborns (ELGAN) Study is a longitudinal study of children born <28 weeks gestation. At age 15, 670 adolescents completed the Mini-International Neuropsychiatric Interview for Children and Adolescents (MINI-KID), the Youth Self-Report, a disability scale of participation in social roles, and cognitive testing. Parents completed a family psychiatric history questionnaire. RESULTS: The most prevalent psychiatric disorders were anxiety, attention-deficit/hyperactivity disorder, and major depression. More girls met criteria for anxiety than boys. Though 66% of participants did not meet criteria for a psychiatric disorder, 15% met criteria for 1, 9% for 2, and 8% for ≥3 psychiatric disorders. Participants with ≥2 psychiatric disorders were more likely to have repeated a grade, to have an individualized educational program, and to have a lower nonverbal IQ than those with no psychiatric disorders. Participants with any psychiatric disorder were more likely to use psychotropic medications; to have greater cognitive and functional impairment; and to have mothers who were single, were on public health insurance, and had less than a high school education. Finally, a positive family psychiatric history was identified more frequently among adolescents with ≥3 psychiatric disorders. CONCLUSION: Among adolescents born extremely preterm, anxiety, major depression, and attention-deficit/hyperactivity disorder were the most prevalent psychiatric disorders at age 15. Adolescents with >1 psychiatric disorder were at increased risk for multiple functional and participatory challenges.


Subject(s)
Anxiety Disorders , Depressive Disorder, Major , Adolescent , Anxiety Disorders/epidemiology , Child , Diagnostic and Statistical Manual of Mental Disorders , Female , Gestational Age , Humans , Infant , Infant, Newborn , Longitudinal Studies , Male
6.
J Child Neurol ; 35(7): 485-491, 2020 06.
Article in English | MEDLINE | ID: mdl-32207663

ABSTRACT

BACKGROUND: This study evaluated the effectiveness of a parent-completed questionnaire for detecting seizures in high-risk children. METHODS: A 2-part seizure screen for children up to 12 years of age with suspected autism spectrum disorder, developmental delay, or seizure, was implemented in 12 Massachusetts clinics serving populations with high health disparities. Primary care providers and developmental behavioral pediatricians administered part 1, a brief highly sensitive screen. If the result was positive, a research assistant administered part 2, a more detailed screen with higher specificity. Positive part 2 results prompted a specialized assessment by a pediatric neurologist. Screening data were evaluated for detection of seizures or other diagnoses, reason for conducting the screen, and appointment outcomes. Data analysis included chi-squared tests, percentages for categorical variables, and means for numerical data. RESULTS: Of 207 administered seizure questionnaires, 78% of children screened positive on part 1. Of those, 94% of families completed part 2 by telephone, and 64 individuals screened positive. The screen helped to detect 15 new seizure diagnoses and 35 other neurologic diagnoses. Average time to first scheduled appointment was 23.8 days. The no-show rate was 7%. CONCLUSIONS: The seizure questionnaire effectively identified seizures and other disorders in a diverse population of high-risk children. Broader use of this low-cost screening tool could improve access to care for children with suspected seizures, increase seizure recognition, and help allocate resources more effectively.


Subject(s)
Autism Spectrum Disorder/complications , Developmental Disabilities/complications , Epilepsy/complications , Parents , Seizures/diagnosis , Seizures/etiology , Surveys and Questionnaires/statistics & numerical data , Child , Child, Preschool , Female , Humans , Infant , Male , Massachusetts
7.
J Pediatr ; 210: 81-90.e3, 2019 07.
Article in English | MEDLINE | ID: mdl-31076229

ABSTRACT

OBJECTIVES: To examine elevated neonatal inflammatory and neurotrophic proteins from children born extremely preterm in relation to later childhood brain Magnetic Resonance Imaging volumes and cognition. STUDY DESIGN: We measured circulating inflammation-related proteins and neurotrophic proteins on postnatal days 1, 7, and 14 in 166 children at 10 years of age (73 males; 93 females). Top quartile levels on ≥2 days for ≥3 inflammation-related proteins and for ≥4 neurotrophic proteins defined exposure. We examined associations among protein levels, brain Magnetic Resonance Imaging volumes, and cognition with multiple linear and logistic regressions. RESULTS: Analyses were adjusted for gestational age at birth and sex. Children with ≥3 elevated inflammation-related proteins had smaller grey matter, brain stem/cerebellar, and total brain volumes than those without elevated inflammation-related proteins, adjusted for neurotrophic proteins. When adjusted for inflammation-related proteins, children with ≥4 neurotrophic proteins, compared with children with no neurotrophic proteins, had larger grey matter and total brain volumes. Higher grey matter, white matter, and cerebellum and brainstem volumes were significantly correlated with higher IQ. Grey and white matter volumes were correlated with each other (r = -0.18; P = .021), and cerebellum and brainstem was highly correlated with grey matter (r = 0.55; P < .001) and white matter (r = 0.29; P < .001). Adjusting for other brain compartments, cerebellum and brainstem was associated with IQ (P = .016), but the association with white matter was marginally significant (P = .051). Grey matter was not associated with IQ. After adjusting for brain volumes, elevated inflammation-related proteins remained significantly associated with a lower IQ, and elevated neurotrophic proteins remained associated with a higher IQ. CONCLUSIONS: Newborn inflammatory and neurotrophin protein levels are associated with later brain volumes and cognition, but their effects on cognition are not entirely explained by altered brain volumes.


Subject(s)
Brain/anatomy & histology , Brain/diagnostic imaging , Cognition , Infant, Extremely Premature/blood , Magnetic Resonance Imaging , Biomarkers/blood , Blood Proteins/analysis , Child , Female , Humans , Infant, Newborn , Inflammation/blood , Male , Nerve Growth Factors/blood , Organ Size , Prospective Studies
8.
J Pediatr ; 201: 40-48.e4, 2018 10.
Article in English | MEDLINE | ID: mdl-30029870

ABSTRACT

OBJECTIVES: To test the hypothesis that higher blood levels of neurotrophic proteins (proteins that support neuronal survival and function) in the first 2 weeks of life are associated with a lower risk of cognitive impairment at 10 years. STUDY DESIGN: We evaluated 812 10-year-old children with neonatal blood specimens enrolled in the multicenter prospective Extremely Low Gestational Age Newborn Study, assessing 22 blood proteins collected on 3 days over the first 2 weeks of life. Using latent profile analysis, we derived a cognitive function level based on standardized cognitive and executive function tests. We defined high exposure as the top quartile neurotrophic protein blood level on ≥2 days either for ≥4 proteins or for a specific cluster of neurotrophic proteins (defined by latent class analysis). Multinomial logistic regression analyzed associations between high exposures and cognitive impairment. RESULTS: Controlling for the effects of inflammatory proteins, persistently elevated blood levels of ≥4 neurotrophic proteins were associated with reduced risk of moderate (OR, 0.35; 95% CI, 0.18-0.67) and severe cognitive impairment (OR, 0.22; 95% CI, 0.09-0.53). Children with a cluster of elevated proteins including angiopoietin 1, brain-derived neurotrophic factor, and regulated upon activation, normal T-cell expressed, and secreted had a reduced risk of adverse cognitive outcomes (OR range, 0.31-0.6). The risk for moderate to severe cognitive impairment was least with 0-1 inflammatory and >4 neurotrophic proteins. CONCLUSIONS: Persisting elevations of circulating neurotrophic proteins during the first 2 weeks of life are associated with lowered risk of impaired cognition at 10 years of age, controlling for increases in inflammatory proteins.


Subject(s)
Child Development , Cognition Disorders/blood , Cognition Disorders/epidemiology , Infant, Extremely Premature/blood , Nerve Growth Factors/blood , Angiopoietin-1/blood , Brain-Derived Neurotrophic Factor/blood , Chemokine CCL5/blood , Child , Cognition , Executive Function , Female , Humans , Infant, Newborn , Male , Prospective Studies , Risk , Severity of Illness Index , T-Lymphocytes/metabolism , United States/epidemiology
9.
Pediatr Neurol ; 79: 45-52, 2018 02.
Article in English | MEDLINE | ID: mdl-29310907

ABSTRACT

BACKGROUND: This study aims to determine the prevalence of neurodevelopmental impairments at age ten years among children born extremely preterm (less than 28 weeks gestational age) and to offer a framework for categorizing neurological limitations. METHODS: A multicenter, prospective cohort follow-up study recruited 889 ten-year-old children born from 2002 to 2004. We assessed prevalence of cognitive impairment, measured by intelligent quotient and tests of executive function, cerebral palsy (CP), autism spectrum disorder (ASD), and epilepsy singly and in combination. The three levels of impairment severity were: category I-no major neurodevelopmental impairment; category II-normal cognitive ability with CP, ASD, and/or epilepsy; and category III-children with cognitive impairment. RESULTS: A total 214 of 873 children (25%) had cognitive impairment, 93 of 849 children (11%) had CP, 61 of 857 children (7%) had ASD, and 66 of 888 children (7%) had epilepsy. Further, 19% of all children had one diagnosis, 10% had two diagnoses, and 3% had three diagnoses. Decreasing gestational age was associated with increasing number of impairments (P < 0.001). Half the children with cognitive impairment and one third of children with CP, ASD, or epilepsy had a single impairment. Six hundred one (68% [95% CI, 64.5%-70.7%]) children were in category I, 74 (8% [95% CI, 6.6%-10.3%]) were in category II, and 214 (24% [95% CI 21.7%-27.4%]) were in category III. CONCLUSIONS: Three quarters of children had normal intellect at age ten years; nearly 70% were free of neurodevelopmental impairment. Forty percent of children with impairments had multiple diagnoses.


Subject(s)
Autism Spectrum Disorder/epidemiology , Cerebral Palsy/epidemiology , Cognitive Dysfunction/epidemiology , Epilepsy/epidemiology , Infant, Extremely Premature , Child , Comorbidity , Developmental Disabilities/epidemiology , Follow-Up Studies , Humans , Prospective Studies , Severity of Illness Index
10.
Pediatr Neurol ; 73: 13-19, 2017 Aug.
Article in English | MEDLINE | ID: mdl-28619377

ABSTRACT

OBJECTIVE: We evaluated the incidence of seizures and epilepsy in the first decade of life among children born extremely premature (less than 28 weeks' gestation). METHOD: In a prospective, multicenter, observational study, 889 of 966 eligible children born in 2002 to 2004 were evaluated at two and ten years for neurological morbidity. Complementing questionnaire data to determine a history of seizures, all caregivers were interviewed retrospectively for postneonatal seizures using a validated seizure screen followed by a structured clinical interview by a pediatric epileptologist. A second pediatric epileptologist established an independent diagnosis based on recorded responses of the interview. A third epileptologist determined the final diagnosis when evaluators disagreed (3%). Life table survival methods were used to estimate seizure incidence through ten years. RESULTS: By age ten years, 12.2% (95% confidence interval: 9.8, 14.5) of children had experienced one or more seizures, 7.6% (95% confidence interval: 5.7, 9.5) had epilepsy, 3.2% had seizure with fever, and 1.3% had a single, unprovoked seizure. The seizure incidence increased with decreasing gestational age. In more than 75% of children with seizures, onset was after one year of age. Seizure incidence was comparable in both sexes. Two-thirds of those with epilepsy had other neurological disorders. One third of children with epilepsy were not recorded on the medical history questionnaire. SIGNIFICANCE: The incidence of epilepsy through age ten years among children born extremely premature is approximately 7- to 14-fold higher than the 0.5% to 1% lifetime incidence reported in the general pediatric population. Seizures in this population are under-recognized, and possibly underdiagnosed, by parents and providers.


Subject(s)
Epilepsy/epidemiology , Infant, Extremely Premature , Seizures/epidemiology , Age Factors , Cerebral Palsy/epidemiology , Child , Cognition Disorders/epidemiology , Cognition Disorders/etiology , Epilepsy/diagnostic imaging , Female , Gestational Age , Head/pathology , Humans , Incidence , Male , Neuropsychological Tests , Prospective Studies , Retrospective Studies , Seizures/diagnostic imaging , Ultrasonography
11.
J Pediatr ; 180: 116-123.e1, 2017 01.
Article in English | MEDLINE | ID: mdl-27788929

ABSTRACT

OBJECTIVES: To evaluate whether in children born extremely preterm, indicators of sustained systemic inflammation in the first month of life are associated with cognitive impairment at school age. STUDY DESIGN: A total of 873 of 966 eligible children previously enrolled in the multicenter Extremely Low Gestational Age Newborn Study from 2002 to 2004 were evaluated at age 10 years. We analyzed the relationship between elevated blood concentrations of inflammation-associated proteins in the first 2 weeks ("early elevations"; n = 812) and the third and fourth week ("late elevations"; n = 532) of life with neurocognition. RESULTS: Early elevations of C-reactive protein, tumor necrosis factor-α, interleukin (IL)-8, intercellular adhesion molecule (ICAM)-1, and erythropoietin were associated with IQ values >2 SD below the expected mean (ORs: 2.0-2.3) and with moderate to severe cognitive impairment on a composite measure of IQ and executive function (ORs: 2.1-3.6). Additionally, severe cognitive impairment was associated with late protein elevations of C-reactive protein (OR: 4.0; 95% CI 1.5, 10), IL-8 (OR: 5.0; 1.9, 13), ICAM-1 (OR: 6.5; 2.6, 16), vascular endothelial growth factor-receptor 2 (OR: 3.2; 1.2, 8.3), and thyroid-stimulating hormone (OR: 3.1; 1.3, 7.3). Moderate cognitive impairment was most strongly associated with elevations of IL-8, ICAM-1, and vascular endothelial growth factor-receptor 2. When 4 or more inflammatory proteins were elevated early, the risk of having an IQ <70 and having overall impaired cognitive ability was more than doubled (ORs: 2.1-2.4); the presence of 4 or more inflammatory protein elevated late was strongly linked to adverse cognitive outcomes (ORs: 2.9-4.8). CONCLUSIONS: Extremely preterm children who had sustained elevations of inflammation-related proteins in the first postnatal month are more likely than extremely preterm peers without such elevations to have cognitive impairment at 10 years.


Subject(s)
C-Reactive Protein/analysis , Cognitive Dysfunction/blood , Erythropoietin/blood , Intercellular Adhesion Molecule-1/blood , Interleukin-8/blood , Vascular Endothelial Growth Factor A/blood , Child , Female , Humans , Infant, Extremely Premature , Infant, Newborn , Inflammation/blood , Male , Prospective Studies
12.
J Electrochem Soc ; 156(8): B943-B954, 2009.
Article in English | MEDLINE | ID: mdl-20414470

ABSTRACT

In this study 1-dodecyl-3-methylimidazolium (C(12)mim) bis(pentafluoroethylsulfonyl)imide (BETI) and 1-dodecylimidazolium (C(12)im) BETI hydrophobic room-temperature ionic liquids (RTILs) were synthesized and used as proton-conducting electrolytes in a nonhumidified feed gas electrochemical cell. The ionic conductivities of C(12)mimBETI and C(12)imBETI were similar and increased linearly with an increase in temperature from 20 to 130°C. However, when used in the electrochemical system the protic water-equilibrated C(12)imBETI had a larger maximum current and power density compared to the aprotic water-equilibrated C(12)mimBETI. The effect of water content on the reaction rates and thermodynamics of these hydrophobic RTILs was also examined. The efficiency of the C(12)mimBETI increased upon removal of water while that of the C(12)imBETI decreased in efficiency when water was removed. The water structure in these RTILs was examined using attenuated total internal reflection Fourier transform IR spectroscopy and depended on the chemical structure of the cation. These studies give further insight into the possible mechanism of proton transport in these RTIL systems.

13.
J Phys Chem B ; 111(18): 4990-9, 2007 May 10.
Article in English | MEDLINE | ID: mdl-17441750

ABSTRACT

In this study, we have examined both the effect of alkyl chain length and anion composition on the 1-alkyl-3-methylimidazolium (C(n)mim, n = 4, 6, 8, 10, and 12) structure and orientation at the room-temperature ionic liquid (RTIL)/SiO(2) interface by sum-frequency vibrational spectroscopy (SFVS). Four different anions were investigated in this study: tetrafluoroborate (BF(4)), hexafluorophosphate (PF(6)), bis(trifluoromethylsulfonyl)imide (BMSI), and bis(pentafluoroethylsulfonyl)imide (BETI). It was found that the alkyl chain in BMSI and BETI RTILs showed a decrease in gauche defects with an increase in chain length, whereas the alkyl chains of the BF(4) and PF(6) RTILs have virtually no gauche defects regardless of chain length. The tilt of the alkyl chain lies predominantly perpendicular to the surface for all the RTILs examined. A strong correlation between the HCCH vs tilt angle and alkyl chain length was observed; as the alkyl chain is lengthened the HCCH vs lies more perpendicular to the SiO(2) surface. The results of this study suggest that the length of the alkyl chain dictates to a large degree the orientation of the imidazolium cation at the surface, regardless of anion composition. To a lesser extent, the HCCH vs tilt of the imidazolium ring of the cation also appears to be correlated to the surface charge density of the SiO(2). As the SiO(2) surface charge density becomes more negative the HCCH vs tilt angle lies more parallel to the surface.

14.
Langmuir ; 21(26): 12179-86, 2005 Dec 20.
Article in English | MEDLINE | ID: mdl-16342990

ABSTRACT

The surface and aqueous interfacial tensions for a series of water-immiscible room-temperature ionic liquids (RTILs) have been measured. The RTILs used in this study were based on 1-alkyl-3-methylimidazolium cations (Cnmim, n=6, 8, 10, and 12) and bis(perfluoromethylsulfonyl)imide (BMSI) and bis(perfluoroethylsulfonyl)imide (BETI) anions. It was found that the surface tensions of the RTILs increased with an increasing cation chain length similar to the behavior of n-alkanes. Interfacial tensions of the RTILs with aqueous solutions, however, were found to decrease with the cation chain length, which has been attributed to the increased surface activity of the longer chain cations. We have also demonstrated the first use of electrocapillary measurements to study the polarizable RTIL/aqueous interfaces. From the electrocapillary data, the potential of zero charge (PZC) for these RTIL/aqueous interfaces was determined, as well as the relative surface excess charge and capacitance. The PZC was found to be dependent upon the structure of the anions and cations with PZC values ranging from -357 mV for C6mimBETI and -161 mV for C10mimBMSI. The electrocapillary results also show that the cations of the RTIL are becoming increasingly surface-active as the alkyl chain on the cation is lengthened, thereby modulating the interfacial potential.

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