Molecular interpretation of low-temperature heat capacity of aliphatic oligo-urethane

Czerniecka‐Kubicka, Anna; Zarzyka, Iwona; Walczak, Małgorzata; Schliesser, Jacob; Popovic, Marko; Woodfield, Brian F.; Pyda, M.

doi:10.1016/j.jct.2017.05.019

Cited by 9 publications

(5 citation statements)

References 19 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…For calibrated heat capacity data, three measurements were performed: a blank/reference, a calibration with sapphire, and the examinee sample. On this basis, the heat capacity, at a steady state, was determined from the following equation [ 69 , 70 ]:

where K is Newton’s constant, ΔT is the temperature difference between reference and sample, C s is the heat capacity of the sample calorimeter including sample and aluminum pan, T s is the temperature of the sample, and q is the heating rate [ 71 ]. The masses of the samples used for measurements were 10–30 mg.…”

Section: Methodsmentioning

confidence: 99%

See 1 more Smart Citation

Long-Term Physical Aging Tracked by Advanced Thermal Analysis of Poly(N-Isopropylacrylamide): A Smart Polymer for Drug Delivery System

2020

View full text Add to dashboard Cite

Poly(N-isopropylacrylamide) (PNIPA), as a smart polymer, can be applied for drug delivery systems. This amorphous polymer can be exposed on a structural recovery process during the storage and transport of medicaments. For the physical aging times up to one year, the structural recovery for PNIPA was studied by advanced thermal analysis. The structural recovery process occurred during the storage of amorphous PNIPA below glass transition and could be monitored by the differential scanning calorimetry (DSC). The enthalpy relaxation (recovery) was observed as overshoot in change heat capacity at the glass transition region in the DSC during heating scan. The physical aging of PNIPA was studied isothermally at 400.15 K and also in the non-isothermal conditions. For the first time, the structural recovery process was analyzed in reference to absolute heat capacity and integral enthalpy in frame of their equilibrium solid and liquid PNIPA.

show abstract

Section: Methodsmentioning

confidence: 99%

“…where K is Newton's constant, ∆T is the temperature difference between reference and sample, C s is the heat capacity of the sample calorimeter including sample and aluminum pan, T s is the temperature of the sample, and q is the heating rate [71]. The masses of the samples used for measurements were 10-30 mg.…”

Section: Methodsmentioning

confidence: 99%

Long-Term Physical Aging Tracked by Advanced Thermal Analysis of Poly(N-Isopropylacrylamide): A Smart Polymer for Drug Delivery System

2020

View full text Add to dashboard Cite

show abstract

“…In second heating, no peak was observed at that temperature range. The peak presence upon first heating and its lack during second heating proved water evaporation [ 17 , 18 ].…”

Section: Resultsmentioning

confidence: 99%

New Mono- and Diesters with Imidazoquinolinone Ring- Synthesis, Structure Characterization, and Molecular Modeling

et al. 2020

View full text Add to dashboard Cite

The objective of the studies was to synthesize and characterize new mono- and diesters with an imidazoquinolin-2-one ring with the use of 2,3-dihydro-2-thioxo-1H-imidazo[4 ,5-c]-quinolin-4(5H)-ones and ethyl bromoacetate. The products were isolated at high yield and characterized by instrumental methods (IR, 1H-, 13C-, and 15N- NMR, MS-ESI, HR-MS, EA). In order to clarify the places of substitution and the structure of the derivatives obtained, molecular modeling of substrates and products was performed. Consideration of the possible tautomeric structures of the substrates confirmed the existence only the most stable keto form. Based on the free energy of monosubstituted ester derivatives, the most stable form were derivatives substituted at sulfur atom of enolic form the used imidazoquinolones. Enolic form referred only to nitrogen atom no 1. The modeling results were consistent with the experimental data. The HOMO electron densities at selected atoms of each substrate has shown that the most reactive atom is sulfur atom. It explained the formation of monoderivatives substituted at sulfur atom. The diester derivatives of the used imidazoquinolones had second substituent at nitrogen atom no. 3. The new diesters can be used as raw material for synthesis of thermally stable polymers, and they can also have biological activity.

show abstract

“…The value of 11 J °C −1 mol −1 was an average value and depends on the bonds which were naturally different between different kinds of atoms. The ratio of our measured heat capacity increment (ΔC p ) to the contribution of a single mobile unit (11 J °C −1 mol −1 ) allowed an estimation to be made of the total number of mobile units ("beads") in amorphous materials [65,77,78]. This ratio gave a total of 15-16 mobile units ("beads") of PU-MDI, which start to become mobile at the glass transition.…”

Section: Dsc Endothermmentioning

confidence: 98%

Linear polyurethanes with imidazoquinazoline rings: preparation and properties evaluation

et al. 2019

View full text Add to dashboard Cite

In this work, research concerning the synthesis and properties of linear polyurethanes (PUs) with the imidazoquinazoline rings was represented. Reaction conditions of 2,6-bis(2-hydroxyethyl)-1-phenylimida-zo[1,5-c]quinazoline-3,5-dione (BHPIQ) with 1,6-hexamethylene diisocyanate were determined and optimized. These conditions are adapted to reaction of BHPIQ with 4,4′-diphenylmethane diisocyanate and 2,4-toluene diisocyanate. New PUs with imidazoquinazoline rings were characterized by spectral methods (1 H-NMR and IR spectroscopies), which confirm their structures. Their molar masses and dispersity index were measured by size exclusion chromatography method. The wide-angle X-ray scattering and differential scanning calorimetry (DSC) studies have shown that all PUs based on BHPIQ are amorphous. Moreover, thermal properties of PUs were investigated by thermogravimetry analysis, standard DSC, and temperature-modulated DSC methods. During thermogravimetric measurements, the exhaust gases were analyzed by FTIR method. Incorporation of imidazoquinazoline ring into the PU chains escalates their glass transition temperature; thus, their heat resistance was enhanced. Furthermore, their degradation rate and the amount of released degradation products were

show abstract

Molecular interpretation of low-temperature heat capacity of aliphatic oligo-urethane

Cited by 9 publications

References 19 publications

Long-Term Physical Aging Tracked by Advanced Thermal Analysis of Poly(N-Isopropylacrylamide): A Smart Polymer for Drug Delivery System

Long-Term Physical Aging Tracked by Advanced Thermal Analysis of Poly(N-Isopropylacrylamide): A Smart Polymer for Drug Delivery System

New Mono- and Diesters with Imidazoquinolinone Ring- Synthesis, Structure Characterization, and Molecular Modeling

Linear polyurethanes with imidazoquinazoline rings: preparation and properties evaluation

Contact Info

Product

Resources

About