The structural evolutions and kinetics of melt-quenched poly(L-lactic acid) (PLLA) during the process of isothermal physical aging below the glass transition temperature (T(g)) were investigated by time-resolved infrared spectroscopy. The results show that local ordered structure is developed with aging time. Such local ordered structure shows the same characteristic band at 918 cm(-1) as that of the mesomorphic structure formed during the unaxially drawn process of PLLA from the glassy state. On the basis of spectroscopic evidence, we therefore proposed that the so-called local ordered structure formed by physical aging can be ascribed to a kind of mesophase of PLLA. Of particular note, a very small amount of mesophase already exists in the initial state of melt-quenched PLLA sample, whereas it is totally undetectable in the melt-quenched poly(D,L-lactide) (PDLLA) sample. By temperature-dependent IR spectroscopy, it is found that the local ordered structure formed during the physical aging process will be "partially molten" rather than "totally molten" in the temperature region corresponding to the physical aging peak of aged PLLA. Such an observation can explain the phenomenon of physical aging enhanced cold crystallization rate.
Download full-text PDF |
Source |
|---|---|
| http://dx.doi.org/10.1021/jp2087863 | DOI Listing |
Publication Analysis
Top Keywords
Similar Publications
Women Have the Power: When Motor Efficiency Makes the Difference in Older Individuals of the Sardinian Blue Zone.
Physiol Behav
January 2025
Department of Pedagogy, Psychology, Philosophy, University of Cagliari, Via Is Mirrionis 1, 09123 Cagliari, Italy.
This study was mainly aimed at exploring the effect of gender on the patterns of Physical Activty (PA) in older people living in an area of exceptional longevity, the so-called Sardinian Blue Zone. Furthermore, the study intended to investigate the nature of the relationships among PA metrics, cognitive measures, and age. One hundred and nine community-dwelling participants (M = 81.
View Article and Find Full Text PDFExercise and exerkines: Mechanisms and roles in anti-aging and disease prevention.
Exp Gerontol
January 2025
Shanghai anti-doping Laboratory, Shanghai University of Sport, Shanghai 200438, China; Department of Rheumatology and Immunology, Ruijin Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai 200240, China. Electronic address:
Aging is a complex biological process characterized by increased inflammation and susceptibility to various age-related diseases, including cognitive decline, osteoporosis, and type 2 diabetes. Exercise has been shown to modulate mitochondrial function, immune responses, and inflammatory pathways, thereby attenuating aging through the regulation of exerkines secreted by diverse tissues and organs. These bioactive molecules, which include hepatokines, myokines, adipokines, osteokines, and neurokines, act both locally and systemically to exert protective effects against the detrimental aspects of aging.
View Article and Find Full Text PDFChronic Low Back Pain Causal Risk Factors Identified by Mendelian Randomization: a Cross-Sectional Cohort Analysis.
Spine J
January 2025
Department of Orthopaedic Surgery, University of California, San Francisco.
Background Context: There are a number of risk factors- from biological, psychological, and social domains- for non-specific chronic low back pain (cLBP). Many cLBP treatments target risk factors on the assumption that the targeted factor is not just associated with cLBP but is also a cause (i.e, a causal risk factor).
View Article and Find Full Text PDFWHY ARE WE NOT EXPLORING THE POTENTIAL OF LOWER LIMB MUSCLE POWER TO IDENTIFY PEOPLE WITH SARCOPENIA?
Ageing Res Rev
January 2025
Fondazione Policlinico Universitario Agostino Gemelli, IRCCS, Rome, Italy; Department of Geriatrics and Orthopedics, Università Cattolica del Sacro Cuore, Rome, Italy. Electronic address:
Sarcopenia refers to a neuromuscular disease characterized by age-related declines in muscle mass and function. Since Professor Rosenberg first introduced the concept of sarcopenia in 1989, numerous operational paradigms have been proposed, tested, and validated against negative outcomes. The most recent recommendations advocate that dynapenia, or reduced of muscle strength, should be used alongside low muscle mass for the identification of sarcopenia.
View Article and Find Full Text PDFExosomal miR-302b rejuvenates aging mice by reversing the proliferative arrest of senescent cells.
Cell Metab
January 2025
Henan Academy of Sciences, Zhengzhou 450000, China; Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China. Electronic address:
Cellular senescence, a hallmark of aging, involves a stable exit from the cell cycle. Senescent cells (SnCs) are closely associated with aging and aging-related disorders, making them potential targets for anti-aging interventions. In this study, we demonstrated that human embryonic stem cell-derived exosomes (hESC-Exos) reversed senescence by restoring the proliferative capacity of SnCs in vitro.
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!