Geometry and time scale of structural relaxation of poly(n-alkylmethacrylates) above the glass transition is studied by temperature dependent one- and two-dimensional 13C-NMR spectroscopy. The geometry of the isotropization of the polymer backbone as deduced from detailed analysis of spectral line shapes is identified as random angular jumps. Analysis of echo decays confirms that at a given temperature this isotropization can adequately be described with a single correlation time. The results are discussed in terms of conformational memory and local structure recently identified in these polymeric glasses.
Download full-text PDF |
Source |
|---|---|
| http://dx.doi.org/10.1016/j.ssnmr.2004.06.005 | DOI Listing |
Publication Analysis
Top Keywords
Similar Publications
Evolutionary Trajectories of Shoots vs. Roots: Plant Volatile Metabolomes Are Richer but Less Structurally Diverse Belowground in the Tropical Tree Genus .
Plants (Basel)
January 2025
Department of Biological Sciences, Binghamton University, Binghamton, NY 13902, USA.
The breadth and depth of plant leaf metabolomes have been implicated in key interactions with plant enemies aboveground. In particular, divergence in plant species chemical composition-amongst neighbors, relatives, or both-is often suggested as a means of escape from insect herbivore enemies. Plants also experience strong pressure from enemies such as belowground pathogens; however, little work has been carried out to examine the evolutionary trajectories of species' specialized chemistries in both roots and leaves.
View Article and Find Full Text PDFShape Memory Performance and Microstructural Evolution in PLA/PEG Blends: Role of Plasticizer Content and Molecular Weight.
Polymers (Basel)
January 2025
School of Polymer Engineering, Institute of Engineering, Suranaree University of Technology, Nakhon Ratchasima 30000, Thailand.
Poly(lactic acid) (PLA) exhibits excellent shape memory properties but suffers from brittleness and a high glass transition temperature (T), limiting its utility in flexible and durable applications. This study explored the modification of PLA properties through the incorporation of poly(ethylene glycol) (PEG), varying in both content (5-20 wt%) and molecular weight (4000-12,000 g/mol), to enhance its suitability for specific applications, such as medical splints. The PLA/PEG blend, containing 15 wt% PEG and with a molecular weight of 12,000 g/mol, exhibited superior shape fixity (99.
View Article and Find Full Text PDFMagnetically Diluted Dy and Yb Squarates Showing Relaxation Tuning and Matrix Dependence.
Molecules
January 2025
Department of Engineering Science, The University of Electro-Communications, Chofu 182-8585, Tokyo, Japan.
A new compound [Y(sq)(HO)] (Y-sq; sq = squarate (CO)) was prepared and structurally characterized. Since the RE-sq family (RE = Y, Dy, Yb, Lu) gave isostructural crystals, the objective of this study is to explore the effects of diamagnetic dilution on the SIM behavior through systematic investigation and comparison of diamagnetically diluted and undiluted forms. The 1%-Diluted Dy compounds, Dy@Y-sq and Dy@Lu-sq, showed AC magnetic susceptibility peaks without any DC bias field (), whereas undiluted Dy-sq showed no AC out-of-phase response under the same conditions.
View Article and Find Full Text PDFUnlocking Female Fertility with a Specific Reproductive Exercise Program: Protocol of a Randomized Controlled Clinical Trail.
Life (Basel)
December 2024
Workgroup for Science Management, Semmelweis University Doctoral College, 1085 Budapest, Hungary.
According to World Health Organization (WHO) data, 16% of people are affected by infertility across the globe. One underlying factor is the age-related decline of ovarian reserve (DOR), which can lead to a higher chance of infertility and has no widely accepted treatment currently. Specific supplements and moderate exercise have been shown to improve fertility; however, there is no consensus to date on the type of exercise providing the best results.
View Article and Find Full Text PDFMultistrategic Approaches in the Treatment of Acute Migraine During Pregnancy: The Effectiveness of Physiotherapy, Exercise, and Relaxation Techniques.
Medicina (Kaunas)
December 2024
Obstetrics and Gynaecology, Kayseri City Hospital, 38080 Kayseri, Turkey.
: Migraine is a common neurological condition that significantly impacts quality of life, especially in women during their reproductive years. Pregnancy poses unique challenges for migraine management due to hormonal changes and the limited use of pharmacological treatments. Non-pharmacological interventions, such as physiotherapy, exercise, and relaxation techniques, offer promising alternatives for managing migraines during this critical period.
View Article and Find Full Text PDFWant AI Summaries of new PubMed Abstracts delivered to your In-box?
Enter search terms and have AI summaries delivered each week - change queries or unsubscribe any time!