Modeling the mechanics of covalently adaptable polymer networks with temperature-dependent bond exchange reactions

Soft Matter ◽  
2013 ◽  
Vol 9 (15) ◽  
pp. 4083 ◽  
Author(s):  
Rong Long ◽  
H. Jerry Qi ◽  
Martin L. Dunn
Keyword(s):  
Polymer Networks ◽  
Exchange Reactions ◽  
Temperature Dependent

Impact of dynamic covalent chemistry and precise linker length on crystallization kinetics and morphology in ethylene vitrimers

Soft Matter ◽  
2022 ◽  
Author(s):  
Bhaskar Soman ◽  
Yoo Kyung Go ◽  
Chengtian Shen ◽  
Cecilia Leal ◽  
Christopher M. Evans
Keyword(s):  
Crystal Structure ◽  
Melting Temperature ◽  
Crystallization Kinetics ◽  
Polymer Networks ◽  
Exchange Reactions ◽  
Dynamic Covalent Chemistry ◽  
Linker Length

Vitrimers, dynamic polymer networks with topology conserving exchange reactions, can lead to unusual evolution of the melting temperature and crystal structure of ethylene networks.

The temperature‐dependent ballistic performance and the ductile‐to‐brittle transition in polymer networks

2019 ◽  
Vol 57 (9) ◽  
pp. 511-523 ◽  
Author(s):  
Kevin A. Masser ◽  
Tyler R. Long ◽  
Jian H. Yu ◽  
Daniel B. Knorr ◽  
Mark D. Hindenlang ◽  
...  
Keyword(s):  
Polymer Networks ◽  
Temperature Dependent ◽  
Ballistic Performance ◽  
Brittle Transition ◽  
Ductile To Brittle Transition

scholarly journals Cross-Linked Polythiomethacrylate Esters Based on Naphthalene—Synthesis, Properties and Reprocessing

Materials ◽  
2020 ◽  
Vol 13 (13) ◽  
pp. 3021
Author(s):  
Karolina Fila ◽  
Beata Podkościelna ◽  
Maciej Podgórski
Keyword(s):  
Polymer Networks ◽  
Polymeric Materials ◽  
Exchange Reactions ◽  
Scanning Calorimetry ◽  
Swelling Properties ◽  
Ene Reaction ◽  
Synthesis Properties ◽  
Double Bond Conversion ◽  
Swelling Studies ◽  
Synthesized Materials

Two structurally different aromatic dithioesters were synthesized from two dithiols and methacryloyl chloride. The polymer networks based on methyl methacrylate and/or styrene and the new dimethacrylates were subsequently prepared. The polymerization yields of copolymers were in the range of 95–99%. The thermal and mechanical properties of the copolymers were determined by means of differential scanning calorimetry (DSC), thermogravimetric analysis (TG/DTG), and Shore D hardness. The addition of dithioesters—1,5-NAF-S-Met (or 1,4(1,5)-NAF-CH2S-Met) (from 0.5% to 5%) to MMA- or ST-based polymers results in lowering the glass transition temperature (Tg) by about 8 °C. The thioester-containing polymers based on MMA exhibit lower thermal stability than those with ST. The polythioesters are stable up to 250 °C. The UV/vis spectra and refractive indexes of prepared liquid compositions were also measured. The 1,5-NAF-S-Met (and 1,4(1,5)-NAF-CH2S-Met) improved the refractive index values of ST and MMA compositions. The double bond conversion was also determined for all synthesized materials. The swelling studies of polymers with 20% addition of thioester crosslinkers were investigated. For all polymeric materials with 20% addition of thioesters, depolymerization of the network was carried out by thiol-thioester exchange. The depolymerization products were re-reacted in a thiol-ene reaction with 2-hydroxyethyl methacrylate by thermal initiation. The thiol-ene procedure enabled reprocessing of starting polymers and obtaining new materials characterized by distinctly different thermal, mechanical, and swelling properties. The thiol-ene materials exhibit a lower Shore hardness in the range of 20–50 °Sh, as well as decreased Tg values when compared to starting copolymers. Due to these possible exchange reactions, one can facilely manipulate the properties of the polymers which could lead to the manufacturing of the new products with the desired features. Degradation of the cross-linked structure and recycling of copolymers were also discussed.

The uptake of amino acids and peptides byStreptococcus lactis

1978 ◽  
Vol 45 (1) ◽  
pp. 93-107 ◽  
Author(s):  
G. H. Rice ◽  
F. H. C. Stewart ◽  
A. J. Hillier ◽  
G. R. Jago
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Apparent Size ◽  
Acid Transport ◽  
Exchange Reactions ◽  
Temperature Dependent ◽  
Streptococcus Lactis ◽  
Effects Of Ph ◽  
Size Restriction ◽  
Low Rate

SummaryPeptide and amino acid transport inStreptococcus lactiswas both energy-and temperature-dependent. Separate systems were present for the transport of amino acids, dipeptides and oligopeptides as well as for individual amino acids. Both tri- and tetra-peptides were readily transported while an apparent size restriction at the point of uptake resulted in a relatively low rate of uptake of the pentapeptide. The effects of pH, temperature and salt concentration on the uptake of amino acids and peptides were studied. Exchange reactions played a significant role in the uptake of both peptides and amino acids.

Investigation of thermoreversible polymer networks by temperature dependent size exclusion chromatography

2017 ◽  
Vol 8 (43) ◽  
pp. 6598-6605 ◽  
Author(s):  
Josef Brandt ◽  
Johannes Lenz ◽  
Kai Pahnke ◽  
Friedrich Georg Schmidt ◽  
Christopher Barner-Kowollik ◽  
...  
Keyword(s):  
Size Exclusion Chromatography ◽  
Polymer Networks ◽  
Diels Alder ◽  
Size Exclusion ◽  
Temperature Dependent ◽  
Novel Approach ◽  
Exclusion Chromatography

We introduce a novel approach for studying thermoreversible Diels–Alder networks by Temperature Dependent SEC.

(111) Monocrystalline Nickel Films

1972 ◽  
Vol 30 ◽  
pp. 512-513
Author(s):  
T.E. Pratt ◽  
R.W. Vook
Keyword(s):  
Film Thickness ◽  
Deposition Rate ◽  
Room Temperature ◽  
Narrow Range ◽  
High Vacuum ◽  
Residual Pressure ◽  
Temperature Dependent ◽  
Deposition Parameters ◽  
Transmission Electron ◽  
Substrate Temperatures

(111) oriented thin monocrystalline Ni films have been prepared by vacuum evaporation and examined by transmission electron microscopy and electron diffraction. In high vacuum, at room temperature, a layer of NaCl was first evaporated onto a freshly air-cleaved muscovite substrate clamped to a copper block with attached heater and thermocouple. Then, at various substrate temperatures, with other parameters held within a narrow range, Ni was evaporated from a tungsten filament. It had been shown previously that similar procedures would yield monocrystalline films of CU, Ag, and Au.For the films examined with respect to temperature dependent effects, typical deposition parameters were: Ni film thickness, 500-800 A; Ni deposition rate, 10 A/sec.; residual pressure, 10-6 torr; NaCl film thickness, 250 A; and NaCl deposition rate, 10 A/sec. Some additional evaporations involved higher deposition rates and lower film thicknesses.Monocrystalline films were obtained with substrate temperatures above 500° C. Below 450° C, the films were polycrystalline with a strong (111) preferred orientation.

Sign in / Sign up

Export Citation Format

Share Document