Glass transition and segmental dynamics in thin supported polystyrene films: The role of molecular weight and annealing

2013 ◽  
Vol 566 ◽  
pp. 186-192 ◽  
Author(s):  
Huajie Yin ◽  
Daniele Cangialosi ◽  
Andreas Schönhals
Keyword(s):  
Molecular Weight ◽  
Glass Transition ◽  
Segmental Dynamics

scholarly journals Effect of soft segment molecular weight on the glass transition, crystallinity, molecular mobility and segmental dynamics of poly(ethylene oxide) based poly(urethane–urea) copolymers

RSC Advances ◽  
2017 ◽  
Vol 7 (65) ◽  
pp. 40745-40754 ◽  
Author(s):  
Oguzhan Oguz ◽  
Stefanos A. Koutsoumpis ◽  
Eren Simsek ◽  
Emel Yilgor ◽  
Iskender Yilgor ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Glass Transition ◽  
Ethylene Oxide ◽  
Dielectric Relaxation ◽  
Molecular Mobility ◽  
Soft Segment ◽  
Dielectric Relaxation Spectroscopy ◽  
Segmental Dynamics ◽  
Poly Ethylene Oxide ◽  
Poly Ethylene

The effect of poly(ethylene oxide) (PEO) soft segment molecular weight (Mn= 2000, 4600, 8000 g mol−1) molecular mobility and segmental dynamics of a series of polyurethane–urea copolymers (PU) was investigated by dielectric relaxation spectroscopy.

scholarly journals Structural Arrest and Thermodynamic Scaling in Filler-Reinforced Polymers

2009 ◽  
Vol 82 (2) ◽  
pp. 202-213 ◽  
Author(s):  
C. G. Robertson ◽  
R. Bogoslovov ◽  
C. M. Roland
Keyword(s):  
Glass Transition ◽  
Volume Fraction ◽  
Filler Concentration ◽  
Scaling Exponent ◽  
Segmental Dynamics ◽  
Reinforced Polymers ◽  
Filler Volume Fraction ◽  
Segmental Relaxation ◽  
Filler Network

Abstract The role of small silica particles on the stiffness and glass transition dynamics of polyvinylacetate (PVAc) was examined for filler volume fraction (ϕ) from 0 to 0.28. Whereas the influences of bound polymer and a strain-dependent filler network were clearly noted in the shear properties, the only effect of filler on the bulk modulus was the reduction in deformable polymer. The calorimetric glass transition of PVAc and its dependence on cooling rate were unaltered by the presence of the silica, in agreement with previous dielectric relaxation results. In contrast to the temperature dependence of the segmental dynamics, which was independent of ϕ, the effect of volume on segmental relaxation was amplified by the addition of silica. This resulted in larger values for the thermodynamic scaling exponent (γ), which also increased sharply at the filler concentration corresponding to the development of a percolated filler network.

scholarly journals Adiponectin: Structure, Physiological Functions, Role in Diseases, and Effects of Nutrition

Nutrients ◽  
2021 ◽  
Vol 13 (4) ◽  
pp. 1180
Author(s):  
Kayvan Khoramipour ◽  
Karim Chamari ◽  
Amirhosein Ahmadi Hekmatikar ◽  
Amirhosein Ziyaiyan ◽  
Shima Taherkhani ◽  
...  
Keyword(s):  
Cardiovascular Disease ◽  
Amino Acids ◽  
Molecular Weight ◽  
Energy Regulation ◽  
Treatment Interventions ◽  
Adipose Tissues ◽  
Physiological Functions ◽  
Cellular Events ◽  
Healthy Nutrition

Adiponectin (a protein consisting of 244 amino acids and characterized by a molecular weight of 28 kDa) is a cytokine that is secreted from adipose tissues (adipokine). Available evidence suggests that adiponectin is involved in a variety of physiological functions, molecular and cellular events, including lipid metabolism, energy regulation, immune response and inflammation, and insulin sensitivity. It has a protective effect on neurons and neural stem cells. Adiponectin levels have been reported to be negatively correlated with cancer, cardiovascular disease, and diabetes, and shown to be affected (i.e., significantly increased) by proper healthy nutrition. The present review comprehensively overviews the role of adiponectin in a range of diseases, showing that it can be used as a biomarker for diagnosing these disorders as well as a target for monitoring the effectiveness of preventive and treatment interventions.

Investigating the role of GeO2 in enhancing the thermal stability and proton mobility of proton-conducting phosphate glasses

2021 ◽  
Author(s):  
Takahisa Omata ◽  
Aman Sharma ◽  
Takuya Kinoshita ◽  
Issei Suzuki ◽  
Tomohiro Ishiyama ◽  
...  
Keyword(s):  
Thermal Stability ◽  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Phosphate Glasses ◽  
Proton Mobility ◽  
Proton Conducting

In this study, the effect of GeO2 on the thermal stability and proton mobility (μH) of proton-conducting phosphate glasses was experimentally investigated using 22HO1/2−3NaO1/2−(12−x)LaO3/2−xGeO2−63PO5/2 glasses. Increasing glass transition temperature (Tg)...

The effect of methyl and methoxy substituents on dianilines for a thermosetting polyimide system

2020 ◽  
Vol 32 (7) ◽  
pp. 801-822 ◽  
Author(s):  
John J La Scala ◽  
Greg Yandek ◽  
Jason Lamb ◽  
Craig M Paquette ◽  
William S Eck ◽  
...  
Keyword(s):  
Thermal Stability ◽  
Molecular Weight ◽  
Glass Transition ◽  
Elevated Temperature ◽  
Methyl Substituent ◽  
Glass Transition Temperatures ◽  
High Performing ◽  
Methoxy Substituent ◽  
Acidic Conditions ◽  
Thermal Stability Of

4,4′-Methylenedianiline (MDA) is widely used in high-temperature polyimide resins, including polymerization of monomer reactants-15. The toxicity of MDA significantly limits the manufacturability using this resin. Modifying the substitution and electronics of MDA could allow for the reduction of toxicity while maintaining the high-performing properties of the materials derived from the modified MDA. The addition of a single methyl substituent, methoxy substituent, location of these substituents, and location of the amine relative to the phenolic bridge were modified as were other non-aniline diamines. Various anilines were condensed with paraformaldehyde under acidic conditions to yield dianilines. These dianilines and diamines were reacted with nadic anhydride and 3,3′,4,4′-benzophenonetetracarboxylic dianhydride in methanol to form the polyamic acid oligomers and heated at elevated temperature to form polyimide oligomers. It was found that the molecular weight of the oligomers derived from MDA alternatives was generally lower than that of MDA oligomers resulting in lower glass transition temperatures ( T gs) and degradation temperatures. Additionally, methoxy substituents further reduce the T g of the polymers versus methyl substituents and reduce the thermal stability of the resin. Methyl-substituted alternatives produced polyimides with similar T gs and degradation temperatures. The toxicity of the MDA alternatives was examined. Although a few were identified with reduced toxicities, the alternatives with properties similar to that of MDA also had high toxicities.

Neurofilament phosphorylation

1995 ◽  
Vol 73 (9-10) ◽  
pp. 575-592 ◽  
Author(s):  
Harish C. Pant ◽  
Veeranna
Keyword(s):  
Molecular Weight ◽  
Nervous System ◽  
Nervous Tissue ◽  
Important Determinant ◽  
Neurofilament Proteins ◽  
Neurofilament Phosphorylation ◽  
Axonal Compartment

Neurofilament proteins (NFPs) are highly phosphorylated molecules in the axonal compartment of the adult nervous system. The phosphorylation of NFP is considered an important determinant of filament caliber, plasticity, and stability. This process reflects the function of NFs during the lifetime of a neuron from differentiation in the embryo through long-term activity in the adult until aging and environmental insult leads to pathology and ultimately death. NF function is modulated by phosphorylation–dephosphorylation in each of these diverse neuronal states. In this review, we have summarized some of these properties of NFP in adult nervous tissue, mostly from work in our own laboratory. Identification of sites phosphorylated in vivo in high molecular weight NFP (NF-H) and properties of NF-associated and neural-specific kinases phosphorylating specific sites in NFP are described. A model to explain the role of NF phosphorylation in determining filament caliber, plasticity, and stability is proposed.Key words: neurofilament proteins, phosphorylation, kinases, phosphatases, regulators, inhibitors, multimesic complex, domains.

Sign in / Sign up

Export Citation Format

Share Document