scholarly journals A Molecular Picture for the Thermo-Reversibility of Gels Formed by Isophthalic Acid-Ended Telechelic Polymers

2015 ◽  
Vol 1794 ◽  
pp. 9-14
Author(s):  
Boyu Li ◽  
Joey Kim ◽  
Julie Kornfield
Keyword(s):  
Hydrogen Bonding ◽  
Aggregation Number ◽  
Polymer Concentration ◽  
Isophthalic Acid ◽  
Solution Temperature ◽  
Present System ◽  
Measured Temperature ◽  
Telechelic Polymers ◽  
End Groups ◽  
Molecular Picture

ABSTRACTWe demonstrate that isophthalic acid-ended telechelic poly(1,5-cyclooctadiene)s (A-PCODs) form thermo-reversible gels in non-polar solvent with a unique molecular mechanism for their thermo-reversibility. Like other associative telechelic polymers, A-PCODs form “flower-like” micelles at low concentration and form gels through bridging at higher concentration which exhibit linear viscoelasticity. However, unlike the widely studied hydrophobically end-capped PEOs, A-PCODs show clear thermo-reversibility in viscosity and dynamic modulus around 30 °C due to the hydrogen-bonding end groups. In addition, they differ from other reported thermo-reversible gelators (eg. Pluronics, PNIPAm containing block copolymers, etc.): neither the end group nor the backbone in the present system has a critical solution temperature within the measured temperature range (0 °C to 60 °C), indicating that the present system has a unique mechanism for its thermo-reversibility. To obtain a molecular picture of the mechanism, rheology and small angle neutron scattering (SANS) studies were implemented. Topological changes above the transition temperature (30 °C) were observed in both oscillatory rheology and SANS. SANS reveals that the size of clusters, which are formed by interacting micelles, depends highly on temperature (T) but independent of polymer concentration. These results cannot be explained by current theories on associative telechelic polymers which assume constant and large aggregation number of end groups at all temperatures and concentrations. We hypothesize that the temperature-sensitive sol-gel transition is due to a decrease in aggregation number for T above the critical temperature in our system, and this temperature-dependence of aggregation number is further determined by the chemical structure and hydrogen-bonding property of isophthalic acid ends.

Selective Hydrogen Bonding Controls Temperature Response of Layer-by-Layer Upper Critical Solution Temperature Micellar Assemblies

Soft Matter ◽  
2021 ◽  
Author(s):  
Aliaksei Aliakseyeu ◽  
Victoria Albright ◽  
Danielle Yarbrough ◽  
Samantha Hernandez ◽  
Qing Zhou ◽  
...  
Keyword(s):  
Hydrogen Bonding ◽  
Methacrylic Acid ◽  
Temperature Response ◽  
Solution Temperature ◽  
Layer By Layer ◽  
Critical Solution Temperature ◽  
Hydrogen Bonding Interactions ◽  
Upper Critical Solution Temperature ◽  
Lbl Films

This work establishes a correlation between the selectivity of hydrogen-bonding interactions and the functionality of micelle-containing layer-by-layer (LbL) assemblies. Specifically, we explore LbL films formed by assembly of poly(methacrylic acid)...

Supramolecular Polymer Materials: Chain Extension of Telechelic Polymers Using a Reactive Hydrogen-Bonding Synthon

2000 ◽  
Vol 12 (12) ◽  
pp. 874-878 ◽  
Author(s):  
B. J. B. Folmer ◽  
R. P. Sijbesma ◽  
R. M. Versteegen ◽  
J. A. J. van der Rijt ◽  
E. W. Meijer
Keyword(s):  
Hydrogen Bonding ◽  
Polymer Materials ◽  
Chain Extension ◽  
Supramolecular Polymer ◽  
Telechelic Polymers

Nanostructure and Rheology of Hydrogen-Bonding Telechelic Polymers in the Melt: From Micellar Liquids and Solids to Supramolecular Gels

2014 ◽  
Vol 47 (6) ◽  
pp. 2122-2130 ◽  
Author(s):  
Tingzi Yan ◽  
Klaus Schröter ◽  
Florian Herbst ◽  
Wolfgang H. Binder ◽  
Thomas Thurn-Albrecht
Keyword(s):  
Hydrogen Bonding ◽  
Telechelic Polymers ◽  
Supramolecular Gels

Synthesis and Characterization of A2+B4 Hyperbranched Polyesters with Hydroxyl End Groups

2014 ◽  
Vol 937 ◽  
pp. 80-85 ◽  
Author(s):  
Haroon A.M. Saeed ◽  
Yassir A. Eltahir ◽  
Yu Min Xia ◽  
Yi Min Wang
Keyword(s):  
Weight Loss ◽  
Isophthalic Acid ◽  
Synthesis And Characterization ◽  
Degree Of Branching ◽  
H Nmr ◽  
Hyperbranched Polyesters ◽  
Melt Polycondensation ◽  
End Groups ◽  
C Nmr

Hydroxyl-terminated hyperbranched polyesters (HBPET) with aromatic-aliphatic structure were synthesized by melt polycondensation of isophthalic acid and pentaerythritol via A2+ B4 approach, at three different monomer mole ratios (A2/B4 =1:1, 1.5:1, 2:1, respectively). Fourier transform infrared (FTIR) spectroscopy indicated that the expected HBPET. The degree of branching of the HBPET was estimated to be between 0.39–0.45 by 1H-NMR and 13C-NMR measurement. The thermogravimetric analysis ( TGA ) measurement revealed that HBPET had a 10 % weight-loss at 350°C in N2.

scholarly journals Narrow equilibrium window for complex coacervation of tau and RNA under cellular conditions

2018 ◽  
Author(s):  
Yanxian Lin ◽  
James McCarty ◽  
Jennifer N. Rauch ◽  
Kris T. Delaney ◽  
Kenneth S. Kosik ◽  
...  
Keyword(s):  
Phase Diagram ◽  
Electrostatic Interactions ◽  
Driving Forces ◽  
Polymer Concentration ◽  
Equilibrium Phase ◽  
Charge Ratio ◽  
Solution Temperature ◽  
Complex Coacervation ◽  
Experimental Conditions ◽  
Form Complex

AbstractThe conditions that lead to the liquid-liquid phase separation (LLPS) of the tau protein, a microtubule associated protein whose pathological aggregation has been implicated in neurodegenerative disorders, are not well understood. Establishing a phase diagram that delineates the boundaries of phase co-existence is key to understanding its LLPS. Using a combination of EPR, turbidity measurements, and microscopy, we show that tau and RNA form complex coacervates with lower critical solution temperature (LCST) behavior. The coacervates are reversible, and the biopolymers can be driven to the supernatant phase or coacervate phase by varying the experimental conditions (temperature, salt concentration, tau:RNA charge ratio, total polymer concentration and osmotic stress). Furthermore, the coacervates can be driven to a fibrillar state through the addition of heparin. The equilibrium phase diagram of the tau/RNA complex coacervate system can be described by a Flory-Huggins model, augmented by an approximate Voorn Overbeek electrostatic term (FH-VO), after fitting the experimental data to an empirical Flory interaction parameter divided into an entropic and enthalpic term. However, a more advanced model in which tau and RNA are treated as discrete bead-spring chains with a temperature-dependent excluded volume interaction and electrostatic interactions between charged residues, investigated through field theoretic simulations (FTS), provided direct and unique insight into the thermodynamic driving forces of tau/RNA complexation. FTS corroborated the experimental finding that the complex coacervation of tau and RNA is has an entropy-driven contribution, with a transition temperature around the physiological temperature of 37 °C and salt concentrations around 100-150 mM. Together, experiment and simulation show that LLPS of tau can occur under physiological cellular conditions, but has a narrow equilibrium window over experimentally tunable parameters including temperature, salt and tau concentrations. Guided by our phase diagram, we show that tau can be driven towards LLPS under live cell coculturing conditions with rationally chosen experimental parameters.

scholarly journals Upper Critical Solution Temperature (UCST) Behavior of Polystyrene-Based Polyampholytes in Aqueous Solution

Polymers ◽  
2019 ◽  
Vol 11 (2) ◽  
pp. 265 ◽  
Author(s):  
Komol Kanta Sharker ◽  
Yuki Ohara ◽  
Yusuke Shigeta ◽  
Shinji Ozoe ◽  
Shin-ichi Yusa
Keyword(s):  
Pure Water ◽  
Polymer Concentration ◽  
Degree Of Polymerization ◽  
Solution Temperature ◽  
Sulfonate Group ◽  
Trimethylammonium Chloride ◽  
Critical Solution Temperature ◽  
Reversible Addition ◽  
Upper Critical Solution Temperature ◽  
Quaternary Ammonium Group

Strong polyampholytes comprising cationic vinylbenzyl trimethylammonium chloride (VBTAC) bearing a pendant quaternary ammonium group and anionic sodium p-styrenesulfonate (NaSS) bearing a pendant sulfonate group were prepared via reversible addition-fragmentation chain-transfer polymerization. The resultant polymers are labelled P(VBTAC/NaSS)n, where n indicates the degree of polymerization (n = 20 or 97). The percentage VBTAC content in P(VBTAC/NaSS)n is always about 50 mol%, as revealed by 1H NMR measurements, meaning that P(VBTAC/NaSS)n is a close to stoichiometrically charge-neutralized polymer. Although P(VBTAC/NaSS)n cannot dissolve in pure water at room temperature, the addition of NaCl or heating solubilizes the polymers. Furthermore, P(VBTAC/NaSS)n exhibits upper critical solution temperature (UCST) behavior in aqueous NaCl solutions. The UCST is shifted to higher temperatures by increasing the polymer concentration and molecular weight, and by decreasing the NaCl concentration. The UCST behavior was measured ranging the polymer concentrations from 0.5 to 5.0 g/L.

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