scholarly journals Anomalous Thermal Characteristics of Poly(Ionic Liquids) Derived from 1-Butyl-2,3-dimethyl-4-vinylimidazolium Salts

Polymers ◽  
2022 ◽  
Vol 14 (2) ◽  
pp. 254
Author(s):  
Fan Yang ◽  
Meng Zhao ◽  
Darren Smith ◽  
Peggy Cebe ◽  
Sam Lucisano ◽  
...  
Keyword(s):  
Glass Transition ◽  
Thermal Characteristics ◽  
Attractive Potential ◽  
Glass Transition Temperatures ◽  
Ionic Polymer ◽  
Methyl Group ◽  
Anion Substitution ◽  
Counter Ions ◽  
Anions And Cations ◽  
Anion Type

The synthesis of 1-butyl-2,3-dimethyl-4-vinylimidazolium triflate, its polymerization, and ion exchange to yield a trio of 1-butyl-2,3-dimethyl-4-vinylimidazolium polymers is described. Irrespective of the nature of the anion, substitution at the 2-position of the imidazolium moiety substantially increases the distance between the anion and cation. The methyl substituent at the 2-position also served to expose the importance of H-bonding for the attractive potential between imidazolium moiety and anions in polymers without a methyl group at the 2-position. The thermal characteristics of poly(1-butyl-2,3-dimethyl-4-vinylimidazolium) salts and corresponding poly(1-ethyl-3-methyl-4-vinylimidazolium) salts were evaluated. While the mid-point glass transition temperatures, Tg-mid, for 1-ethyl-3-methyl-4-vinylimidazolium polymers with CF3SO3−, (CF3SO2)2N− and PF6− counterions, were 153 °C, 88 °C and 200 °C, respectively, the Tg-mid values for 1-butyl-2,3-dimethyl-4vinylimidazolium polymers with corresponding counter-ions were tightly clustered at 98 °C, 99 °C and 84 °C, respectively. This dramatically reduced influence of the anion type on the glass transition temperature was attributed to the increased distance between the center of the anions and cations in the 1-butyl-2,3-dimethyl-4-vinylimidazolium polymer set, and minimal H-bonding interactions between the respective anions and the 1-butyl-2,3-dimethyl-4-vinylimidazolium moiety. It is believed that this is the first observation of substantial independence of the glass transition of an ionic polymer on the nature of its counterion.

Relationships between Moisture Content and Physical Properties of Korean Honeys

2010 ◽  
Vol 6 (6) ◽  
Author(s):  
Mi-Jung Kim ◽  
Jun-Hwan Oh ◽  
Byoungseung Yoo
Keyword(s):  
Glass Transition ◽  
Moisture Content ◽  
Loss Modulus ◽  
Thermal Characteristics ◽  
Small Deformation ◽  
Rheological Parameters ◽  
Subzero Temperature ◽  
Physical Parameters ◽  
Transition Temperatures ◽  
Glass Transition Temperatures

Dynamic rheological and thermal characteristics of ten Korean acacia honeys with different moisture contents (18.4 to 20.4 percent) were evaluated as a function of moisture content using both a controlled stress rheometer for small-deformation oscillatory measurements and a differential scanning calorimeter (DSC). The honey samples displayed a liquid-like behavior at a subzero temperature (-5°C) with loss modulus (G") predominating over storage modulus (G'), showing a high dependence on frequency. Plots of dynamic moduli (G' and G") and complex viscosity (?*) versus moisture content gave better exponential relationships (R2 = 0.95-0.97) than the tan delta values (R2 = 0.89). Glass transition temperatures at onset (To) showed a better linear relationship (R2 = 0.87) with moisture content compared to those at midpoint (Tm) (R2 = 0.84) and endpoint (Te) (R2 = 0.81). The dynamic rheological parameters more closely correlated with moisture content as compared to the glass transition temperatures, indicating that dynamic rheological measurements at a subzero temperature are better physical parameters to estimate the quality of honeys.

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.

Properties of Random PSF/PES Copolymers as High-Performance Polymers

2011 ◽  
Vol 217-218 ◽  
pp. 1606-1610
Author(s):  
Dong Jiang ◽  
Xiao Ran Zhang ◽  
Yan Mei Ma ◽  
Cheng You Ma
Keyword(s):  
Weight Loss ◽  
Tensile Strength ◽  
Glass Transition ◽  
High Performance ◽  
Molar Ratio ◽  
Transition Temperatures ◽  
Elongation At Break ◽  
Glass Transition Temperatures ◽  
High Performance Polymers ◽  
Diphenyl Sulfone

A series of random polysulfone/polyethersulfone (PSF/PES) copolymers were synthesized by the polycondensation of 4, 4'-isopropylidendiphenol, 4, 4΄-dihyolroxy diphenyl sulfone and 4, 4'-dichlorodiphenyl sulfone in the presence of K2CO3. We obtained a series of copolymers by changing the molar ratio of 4, 4΄-dihyolroxy diphenyl sulfone and 4, 4'-isopropylidendiphenol (it was marked as the ratio of S:A). The copolymers have the similar solubility with polyethersulfone. They also have high glass transition temperatures (Tg: 199°C~229°C) and 5% weight loss temperatures (4, 4'-isopropylidendiphenol: 4, 4΄-dihyolroxy diphenyl sulfone=1:1, Td5=497°C). At the same time the elongation at break is much higher than that of PES, while the tensile strength is a little lower than that of PES.

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