We investigate the interfacial interactions and segmental dynamics of hydrophilic and hydrophobic (calcined) silica nanoparticle (NP) filled poly(vinyl acetate) (PVAc) composites via a combination of Fourier transform infrared spectroscopy (FTIR) and broadband dielectric spectroscopy measurements. For hydrophilic silica NP filled composites, an increase in the amount of bound carbonyl groups with increasing silica loading can be noted due to hydrogen bonding interactions with hydroxyls on the NP surfaces and carbonyl groups of PVAc. It is surprising that the apparent glass transition temperature (T g ) increases very slightly (∼1 K) compared to pure PVAc, but the glass transition process becomes much broader, indicating the existence of a slower relaxation mode. In addition to the bulklike α-relaxation assigned to polymer segments away from the NP surfaces, the nanocomposites also exhibit a slower interfacial α′-relaxation by 3−4 orders of magnitude compared to bulk polymers. However, in the case of hydrophobic (calcined) silica NP filled composites, T g shifts to higher temperatures by 4−5 K even if there is the absence of strong polymer-NP interfacial interactions confirmed by the FTIR results. Consequently, the overall α-relaxation dynamics are suppressed in the presence of silica NPs, which is attributed to an increase of steric hindrance and decrease of free volume. More importantly, in the nanocomposites with high NP loadings, it is worth noting a weak physical adsorption interfacial layer for which the segmental mobility is on average slower by 1−2 orders of magnitude relative to that for bulk polymers. However, the dielectric strength and interfacial bound fraction is much smaller than that of hydrophilic silica NP filled composites, indicating the fact that physical adsorption is much weaker compared to hydrogen bonding.

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The goal of this study was to evaluate a complex theoretical model linking gender, unsociability, peer relations, and indices of psychological maladjustment among children in the People's Republic of China. Participants were 711 (395 boys) Grade 4 to Grade 8 (M age = 10.98 years, SD = 1.56) students selected from 4 public schools in Shanghai. Multisource assessments were employed, including peer nominations of unsociability, sociometric nominations to measure peer preference, as well as child self-reports of friendship quality, depressive symptoms, loneliness, and self-worth. Among the results, both peer preference and friendship quality mediated the associations between unsociability and psychological maladjustment. Further analyses revealed that such mediating effects were significantly moderated by gender. Specifically, the mediating effects of friendship quality in the associations between unsociability and psychological maladjustment only existed for boys. In addition, peer preference played a mediation role in the associations between unsociability and psychological maladjustment for both boys and girls, although the strength of the associations was stronger among boys than girls. Findings are discussed in terms of the importance of considering gender and different types of peer experiences in studies of unsociable children in Mainland China. | 1015 BULLOCK et aL.

BackgroundMany studies on parental involvement in their children’s education have limitations in cross‐sectional designs in spite of examining the relationships between this involvement and achievement goal orientations. Thus, little is known about whether and how parental involvement affects achievement goal orientations over time.AimsThis study examines the influence of parental involvement on achievement goal orientations among Chinese high school students.SampleThe participants included 741 high school students (367 girls; Mage = 15.51 years, SD = .46) in China.MethodsThe data were collected in five waves with a 6‐month interval, starting in the autumn of tenth grade and ending in the autumn of twelfth grade. In each wave, participants reported their perceived degree of parental involvement, mastery goal orientation, performance‐approach goal orientation and performance‐avoidance goal orientation.ResultsOver time, a decline was seen in these high school students’ perceived level of parental involvement and mastery goal orientation, while an increase in their performance‐approach goal orientation and stability in terms of their performance‐avoidance goal orientation were found. In addition, the results indicated that the level of and changes in parental involvement had significant effects on the changes in mastery goal orientation, and were unrelated to those of two performance goal orientations.ConclusionsThese findings evidence the dynamic nature of parental involvement and students’ achievement goal orientations, as well as the positive influence of such involvement on the endorsement and development of mastery goal orientation, while this was not the case for the other two performance goal orientations.

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