Thermo-Reversible Hybrid Gels Formed from the Combination of Isotactic Polystyrene and [Fe(II) (4-Octadecyl-1,2,4-Triazole)3(ClO4)2]n Metallo-Organic Polymer: Thermal and Viscoelastic Properties

Nano-sized one-dimensional metallo-organic polymers, characterized by the phenomenon of spin transition, are excellent candidates for advanced technological applications such as optical sensors, storage, and information processing devices. However, the main drawback of this type of polymers is their fragile mechanical properties, which hinders its processing and handling, and makes their practical use unfeasible. To overcome this problem, in this work, hybrid thermo-reversible gels are synthesized by combination of a metallo-organic polymer and isotactic polystyrene (iPS) in cis-decaline. A detailed investigation of the thermal and viscoelastic properties of the hybrid gels, in terms of iPS and metallo-organic polymer concentration is performed by means of differential scanning calorimetry and oscillatory rheology, respectively. From the analysis of the thermal properties, three transitions have been determined upon heating: Monotectic transition of the iPS gel, melting of the iPS gel, and melting of the metal-organic polymer gel, which suggest that the gels of the two polymers are formed independently in the hybrid gel, as long as the two polymers are in concentrations above the corresponding critical gelation concentrations. Results regarding viscoelastic properties and morphology confirmed that hybrid gels consisted of an interpenetrated network of polymer gels, formed by iPS and metallo-organic poymer gels growing independently.

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The Influence of the Addition of Nuts on the Thermal and Rheological Properties of Wheat Flour

Molecules ◽

10.3390/molecules26133969 ◽

2021 ◽

Vol 26 (13) ◽

pp. 3969

Author(s):

Karolina Pycia ◽

Lesław Juszczak

Keyword(s):

Rheological Properties ◽

Wheat Flour ◽

Viscoelastic Properties ◽

Control Sample ◽

Scanning Calorimetry ◽

Creep And Recovery ◽

Research Material ◽

Pasting Characteristics ◽

Tan Δ ◽

Weak Gels

The aim of the study was to assess the influence of replacing wheat flour with hazelnuts or walnuts, in various amounts, on the thermal and rheological properties of the obtained systems. The research material were systems in which wheat flour was replaced with ground hazelnuts (H) or walnuts (W) in the amount of 5%, 10%, and 15%. The parameters of the thermodynamic gelatinization characteristics were determined by the differential scanning calorimetry method. In addition, the pasting characteristics were determined with the use of a viscosity analyzer and the viscoelastic properties were assessed. Sweep frequency and creep and recovery tests were used to assess the viscoelastic properties of the tested gels. It was found that replacing wheat flour with nuts increased the values of gelatinization temperature, gelatinization, and retrogradation enthalpy, and the degree of retrogradation. The highest viscosity was characteristic of the control sample (2039 mPa·s), and the lowest for the paste with 15% addition of walnuts (1120 mPa·s). Replacing the flour with nuts resulted in a very visible reduction in the viscosity of such systems. In addition, gels based on the systems with the addition of H and W were weak gels (tan δ = G″/G′ > 0.1), and the values of G′ and G″ parameters decreased with the increased share of nuts in the systems. Creep and recovery analysis indicated that the systems in which wheat flour was replaced with hazelnuts were less susceptible to deformation compared to the systems with the addition of W.

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Li-Nafion Membrane Plasticised with Ethylene Carbonate/Sulfolane: Influence of Mixing Temperature on the Physicochemical Properties

Polymers ◽

10.3390/polym13071150 ◽

2021 ◽

Vol 13 (7) ◽

pp. 1150

Author(s):

Aigul S. Istomina ◽

Tatyana V. Yaroslavtseva ◽

Olga G. Reznitskikh ◽

Ruslan R. Kayumov ◽

Lyubov V. Shmygleva ◽

...

Keyword(s):

Physicochemical Properties ◽

Ethylene Carbonate ◽

Membrane Integrity ◽

Amorphous Structure ◽

Nafion Membrane ◽

Polymer Gel ◽

Scanning Calorimetry ◽

Practical Applications ◽

Heating And Cooling ◽

Solvent Uptake

The use of dipolar aprotic solvents to swell lithiated Nafion ionomer membranes simultaneously serving as electrolyte and separator is of great interest for lithium battery applications. This work attempts to gain an insight into the physicochemical nature of a Li-Nafion ionomer material whose phase-separated nanostructure has been enhanced with a binary plasticiser comprising non-volatile high-boiling ethylene carbonate (EC) and sulfolane (SL). Gravimetric studies evaluating the influence both of mixing temperature (25 to 80 °C) and plasticiser composition (EC/SL ratio) on the solvent uptake of Li-Nafion revealed a hysteresis between heating and cooling modes. Differential scanning calorimetry (DSC) and wide-angle X-ray diffraction (WAXD) revealed that the saturation of a Nafion membrane with such a plasticiser led to a re-organisation of its amorphous structure, with crystalline regions remaining practically unchanged. Regardless of mixing temperature, the preservation of crystallites upon swelling is critical due to ionomer crosslinking provided by crystalline regions, which ensures membrane integrity even at very high solvent uptake (≈200% at a mixing temperature of 80 °C). The physicochemical properties of a swollen membrane have much in common with those of a chemically crosslinked polymer gel. The conductivity of ≈10−4 S cm−1 demonstrated by Li-Nafion membranes saturated with EC/SL at room temperature is promising for various practical applications.

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Formulation and Evaluation of Benidipine Nanosuspension

Research Journal of Pharmacy and Technology ◽

10.52711/0974-360x.2021.00712 ◽

2021 ◽

pp. 4111-4116

Author(s):

Sejal Patel ◽

Anita P. Patel

Keyword(s):

Particle Size ◽

Water Solubility ◽

Polymer Concentration ◽

Oral Route ◽

Water Soluble ◽

In Vitro Dissolution ◽

Scanning Calorimetry ◽

23 Factorial Design ◽

Selection Of

In the interest of administration of dosage form oral route is most desirable and preferred method. After oral administration to get maximum therapeutic effect, major challenge is their water solubility. Water insoluble drug indicate insufficient bioavailability as well dissolution resulting in fluctuating plasma level. Benidipine (BND) is poorly water soluble antihypertensive drug has lower bioavailability. To improve bioavailability of Benidipine HCL, BND nanosuspension was formulated using media milling technique. HPMC E5 was used to stabilize nanosuspension. The effect of different important process parameters e.g. selection of polymer concentration X1(1.25 mg), stirring time X2 (800 rpm), selection of zirconium beads size X3 (0.4mm) were investigated by 23 factorial design to accomplish desired particle size and saturation solubility. The optimized batch had 408 nm particle size Y1, and showed in-vitro dissolution Y2 95±0.26 % in 30 mins and Zeta potential was -19.6. Differential scanning calorimetry (DSC) and FT-IR analysis was done to confirm there was no interaction between drug and polymer.

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Morphological basis for the complex melting behaviour of isotactic polystyrene

e-Polymers ◽

10.1515/epoly.2002.2.1.544 ◽

2002 ◽

Vol 2 (1) ◽

Author(s):

Mahmoud Al-Hussein ◽

Gert Strobl

Keyword(s):

Morphological Changes ◽

Melting Behaviour ◽

Temperature Dependent ◽

Molten Material ◽

Scanning Calorimetry ◽

Isotactic Polystyrene ◽

X Ray ◽

Long Period ◽

X Ray Scattering ◽

Increasing Temperature

AbstractTemperature-dependent small-angle X-ray scattering spectroscopy of isothermally cold crystallized isotactic polystyrene revealed considerable morphological reorganization during subsequent heating to the melt. Both the crystalline thickness and the long period increased continuously with increasing temperature before the samples finally melted. The temperature dependence of these changes correlated very well with the melting behaviour observed with differential scanning calorimetry. As the temperature increased during a heating scan, the initial lamellae that formed during isothermal crystallization showed only little reorganization until they started to melt. Then, the molten material recrystallized continuously into increasingly thicker lamellae at increasing temperature until they finally melted. As the crystallization temperature approached the final melting temperature of the recrystallized lamellae, the initial lamellae melted without further recrystallization and no morphological changes were seen in this case.

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Development and Characterization of pH-Dependent Cellulose Acetate Phthalate Nanofibers by Electrospinning Technique

Nanomaterials ◽

10.3390/nano11123202 ◽

2021 ◽

Vol 11 (12) ◽

pp. 3202

Author(s):

Gustavo Vidal-Romero ◽

Virginia Rocha-Pérez ◽

María L. Zambrano-Zaragoza ◽

Alicia Del Real ◽

Lizbeth Martínez-Acevedo ◽

...

Keyword(s):

Cellulose Acetate ◽

Polymer Concentration ◽

Process Efficiency ◽

Fickian Diffusion ◽

Solvent Mixtures ◽

Cellulose Acetate Phthalate ◽

Scanning Calorimetry ◽

Electrospinning Technique ◽

Ph Dependent ◽

Release Profiles

The aim of this work was to obtain pH-dependent nanofibers with an electrospinning technique as a novel controlled release system for the treatment of periodontal disease (PD). Cellulose acetate phthalate (CAP) was selected as a pH-sensitive and antimicrobial polymer. The NF was optimized according to polymeric dispersion variables, polymer, and drug concentration, and characterized considering morphology, diameter, entrapment efficiency (EE), process efficiency (PE), thermal properties, and release profiles. Two solvent mixtures were tested, and CHX-CAP-NF prepared with acetone/ethanol at 12% w/v of the polymer showed a diameter size of 934 nm, a uniform morphology with 42% of EE, and 55% of PE. Meanwhile, CHX-CAP-NF prepared with acetone/methanol at 11% w/v of polymer had a diameter of 257 nm, discontinuous nanofiber morphology with 32% of EE, and 40% of PE. EE and PE were dependent on the polymer concentration and the drug used in the formulation. Studies of differential scanning calorimetry (DSC) showed that the drug was dispersed in the NF matrix. The release profiles of CHX from CHX-CAP-NF followed Fickian diffusion dependent on time (t0.43−0.45), suggesting a diffusion–erosion process and a matrix behavior. The NF developed could be employed as a novel drug delivery system in PD.

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Structural and Viscoelastic Properties of Thermoplastic Polyurethanes Containing Mixed Soft Segments with Potential Application as Pressure Sensitive Adhesives

Polymers ◽

10.3390/polym13183097 ◽

2021 ◽

Vol 13 (18) ◽

pp. 3097

Author(s):

Mónica Fuensanta ◽

José Miguel Martín-Martínez

Keyword(s):

Phase Separation ◽

Potential Application ◽

Viscoelastic Properties ◽

Gravimetric Analysis ◽

Scanning Calorimetry ◽

Adhesion Properties ◽

Pressure Sensitive Adhesives ◽

Thermoplastic Polyurethanes ◽

Pressure Sensitive ◽

Soft Segments

Thermoplastic polyurethanes (TPUs) were synthetized with blends of poly(propylene glycol) (PPG) and poly(1,4-butylene adipate) (PAd) polyols, diphenylmethane-4,4′-diisocyanate (MDI) and 1,4-butanediol (BD) chain extender; different NCO/OH ratios were used. The structure and viscoelastic properties of the TPUs were assessed by infrared spectroscopy, differential scanning calorimetry, X-ray diffraction, thermal gravimetric analysis and plate-plate rheology, and their pressure sensitive adhesion properties were assessed by probe tack and 180° peel tests. The incompatibility of the PPG and PAd soft segments and the segregation of the hard and soft segments determined the phase separation and the viscoelastic properties of the TPUs. On the other hand, the increase of the NCO/OH ratio improved the miscibility of the PPG and PAd soft segments and decreased the extent of phase separation. The temperatures of the cool crystallization and melting were lower and their enthalpies were higher in the TPU made with NCO/OH ratio of 1.20. The moduli of the TPUs increased by increasing the NCO/OH ratio, and the tack was higher by decreasing the NCO/OH ratio. In general, a good agreement between the predicted and experimental tack and 180° peel strength values was obtained, and the TPUs synthesized with PPG+PAd soft segments had potential application as pressure sensitive adhesives (PSAs).

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Balanced Viscoelastic Properties of Pressure Sensitive Adhesives Made with Thermoplastic Polyurethanes Blends

Polymers ◽

10.3390/polym11101608 ◽

2019 ◽

Vol 11 (10) ◽

pp. 1608 ◽

Cited By ~ 3

Author(s):

Fuensanta ◽

Vallino-Moyano ◽

Martín-Martínez

Keyword(s):

Phase Separation ◽

Viscoelastic Properties ◽

Simple Procedure ◽

Peel Strength ◽

Similar Degree ◽

Gravimetric Analysis ◽

Scanning Calorimetry ◽

Pressure Sensitive Adhesives ◽

Thermoplastic Polyurethanes ◽

Pressure Sensitive

Pressure sensitive adhesives made with blends of thermoplastic polyurethanes (TPUs PSAs) with satisfactory tack, cohesion, and adhesion have been developed. A simple procedure consisting of the physical blending of methyl ethyl ketone (MEK) solutions of two thermoplastic polyurethanes (TPUs) with very different properties—TPU1 and TPU2—was used, and two different blending procedures have been employed. The TPUs were characterized by infra-red spectroscopy in attenuated total reflectance mode (ATR-IR spectroscopy), differential scanning calorimetry, thermal gravimetric analysis, and plate-plate rheology (temperature and frequency sweeps). The TPUs PSAs were characterized by tack measurement, creep test, and the 180° peel test at 25 °C. The procedure for preparing the blends of the TPUs determined differently their viscoelastic properties, and the properties of the TPUs PSAs as well, the blending of separate MEK solutions of the two TPUs imparted higher tack and 180° peel strength than the blending of the two TPUs in MEK. TPU1 + TPU2 blends showed somewhat similar contributions of the free and hydrogen-bonded urethane groups and they had an almost similar degree of phase separation, irrespective of the composition of the blend. Two main thermal decompositions at 308–317 °C due to the urethane hard domains and another at 363–373 °C due to the soft domains could be distinguished in the TPU1 + TPU2 blends, the weight loss of the hard domains increased and the one of the soft domains decreased by increasing the amount of TPU2 in the blends. The storage moduli of the TPU1 + TPU2 blends were similar for temperatures lower than 20 °C and the moduli at the cross over of the moduli were lower than in the parent TPUs. The improved properties of the TPU1 + TPU2 blends derived from the creation of a higher number of hydrogen bonds upon removal of the MEK solvent, which lead to a lower degree of phase separation between the soft and the hard domains than in the parent TPUs. As a consequence, the properties of the TPU1 + TPU2 PSAs were improved because good tack, high 180° peel strength, and sufficient cohesion were obtained, particularly in 70 wt% TPU1 + 30 wt% TPU2 PSA.

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Effect of Extending Oil on Viscoelastic Behavior of Elastomers

Rubber Chemistry and Technology ◽

10.5254/1.3538155 ◽

1983 ◽

Vol 56 (4) ◽

pp. 784-807 ◽

Cited By ~ 1

Author(s):

N. Nakajima ◽

E. R. Harrell

Keyword(s):

Molecular Weight ◽

Viscoelastic Properties ◽

Polymer Concentration ◽

Viscoelastic Behavior ◽

Chain Structure ◽

Frequency Range ◽

Molecular Weight Polymer ◽

Wide Range ◽

Two Samples ◽

Superposition Principles

Abstract For a number of years, oil-extended elastomers have been in commercial use. The obvious advantage is to dilute elastomers with less expensive oil. In addition, oil improves the processability of the elastomer. This enables the use of a higher-molecular-weight polymer, which, in turn, yields mechanical properties comparable or superior to those of a lower-molecular-weight polymer without oil extension. The viscoelastic properties of the oil-elastomer mixtures at a wide range of concentration and temperature offer information useful for understanding elastomer processability. The viscoelastic properties of such systems are also most sensitive manifestations of the polymer chain structure and, therefore, they represent fundamental characteristics of a given elastomer sample. In this work, two samples of ethylene-propylene copolymer differing in chain structure were selected. The oil-elastomer mixtures were prepared for polymer concentration in the range of 2.5–100%. The viscoelastic properties have been measured in the temperature range of 30–150°C. The frequency range was 10−1–102 rad/s and in some cases −2–102 rad/ s. The superposition principles have been examined with these data for both the temperature and concentration dependence.

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Melting Gel Films for Low Temperature Seals

MRS Proceedings ◽

10.1557/opl.2013.506 ◽

2013 ◽

Vol 1547 ◽

pp. 81-86 ◽

Cited By ~ 1

Author(s):

Mihaela Jitianu ◽

Andrei Jitianu ◽

Michael Stamper ◽

Doreen Aboagye ◽

Lisa C. Klein

Keyword(s):

Room Temperature ◽

Viscous Fluids ◽

Methyl Groups ◽

Scanning Calorimetry ◽

Hybrid Gels ◽

Methyl Group ◽

Oscillatory Rheometry ◽

Melting Gels ◽

Viscous Modulus ◽

Insight Into

ABSTRACTMelting gels are silica-based hybrid gels with the curious behavior that they are rigid at room temperature, but soften around 110°C. A typical melting gel is prepared by mixing methyltriethoxysilane (MTES) and dimethyldiethoxysilane (DMDES). MTES has one methyl group substituted for an ethoxy, and DMDES has two substitutions. The methyl groups do not hydrolyze, which limits the network-forming capability of the precursors. To gain insight into the molecular structure of the melting gels, differential scanning calorimetry and oscillatory rheometry studies were performed on melting gels before consolidation. According to oscillatory rheometry, at room temperature, the gels behave as viscous fluids, with a viscous modulus, G″(t,ω0) that is larger than the elastic modulus, G′(t,ω0). As the temperature is decreased, gels continue to behave as viscous fluids, with both moduli increasing with decreasing temperature. At some point, the moduli cross over, and this temperature is recorded as the glass transition temperature Tg. The Tg values obtained from both methods are in excellent agreement. The Tg decreases from -0.3oC to -56oC with an increase in the amount of di-substituted siloxane (DMDES) from 30 to 50 mole %. A decrease of the Tg follows an increase of the number of hydrolytically stable groups, meaning a decrease in the number of oxygen bridges between siloxane chains.

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