scholarly journals Influence of Cross-Linking Degree on Hydrodynamic Behavior and Stimulus-Sensitivity of Derivatives of Branched Polyethyleneimine

Polymers ◽  
2020 ◽  
Vol 12 (5) ◽  
pp. 1085
Author(s):  
Alina Amirova ◽  
Tatyana Kirila ◽  
Mikhail Kurlykin ◽  
Andrey Tenkovtsev ◽  
Alexander Filippov
Keyword(s):  
Aqueous Solutions ◽  
Mole Fraction ◽  
Solution Temperature ◽  
Linear Polymers ◽  
Intermolecular Hydrogen Bonds ◽  
Critical Solution Temperature ◽  
Cross Linker ◽  
The Cross ◽  
Derivatives Of ◽  
Constant Characteristics

Cross-linked derivatives of acylated branched polyethyleneimine containing 2-isopropyl-2-oxazoline units were investigated in chloroform and aqueous solutions using methods of molecular hydrodynamics, static and dynamic light scattering, and turbidity. The studied samples differed by the cross-linker content. The solubility of the polyethyleneimines studied worsened with the increasing mole fraction of the cross-linker. Cross-linked polyethyleneimines were characterized by small dimensions in comparison with linear analogs; the increase in the cross-linker content leads to a growth of intramolecular density. At low temperatures, the aqueous solutions of investigated samples were molecularly dispersed, and the large aggregates were formed due to the dehydration of oxazoline units and the formation of intermolecular hydrogen bonds. For the cross-linked polyethyleneimines, the phase separation temperatures were lower than that for linear and star-shaped poly-2-isopropyl-2-oxazolines. The low critical solution temperature of the solutions of studied polymers decreased with the increasing cross-linker mole fraction. The time of establishment of the constant characteristics of the studied solutions after the jump-like change in temperature reaches 3000 s, which is at least two times longer than for linear polymers.

scholarly journals Effects of the Hydrophilic–Lipophilic Balance of Alternating Peptides on Self-Assembly and Thermo-Responsive Behaviors

2019 ◽  
Vol 20 (18) ◽  
pp. 4604 ◽  
Author(s):  
Ihsan ◽  
Nargis ◽  
Koyama
Keyword(s):  
Aqueous Solutions ◽  
Self Assembly ◽  
Polymer Chains ◽  
Systematic Evaluation ◽  
Solution Temperature ◽  
Critical Solution Temperature ◽  
Hydrophilic Lipophilic Balance ◽  
Upper Critical Solution Temperature ◽  
Cloud Points ◽  
Micellization Behavior

A series of N-substituted poly(Gly–alter–Val) peptides were successfully synthesized for the systematic evaluation of the micellization behavior of alternating peptides. Three-component polymerization employing an aldehyde, a primary ammonium chloride, and potassium isocyanoacetate afforded four alternating peptides in excellent yields. We investigated the dependence of the hydrophilic–lipophilic balance of alternating peptides on the micellization behavior. All the aqueous solutions of alternating peptides exhibited upper critical solution temperature (UCST) behaviors, strongly indicating that the alternating binary pattern would mainly contribute to the UCST behaviors. The cloud points of alternating peptides shifted to higher temperatures as the side chains became more hydrophilic, which is opposite to the trend of typical surfactants. Such unusual micellization behaviors appeared to be dependent on the quasi-stable structure of single polymer chains formed in water.

Cloud Point Curves of Aqueous Solutions of Poly(N-ethylmethacrylamide)

1993 ◽  
Vol 58 (10) ◽  
pp. 2370-2382 ◽  
Author(s):  
Miloslav Bohdanecký ◽  
Jiří Horský ◽  
Vladimír Petrus ◽  
Libuše Mrkvičková ◽  
Karel Ulbrich
Keyword(s):  
Molecular Weight ◽  
Aqueous Solutions ◽  
Cloud Point ◽  
Threshold Concentration ◽  
Solution Temperature ◽  
Threshold Temperature ◽  
Critical Solution Temperature ◽  
Dilute Solution Properties ◽  
Experimental Errors ◽  
The Difference

Aqueous solutions of poly(N-ethylmethacrylamide) have a lower critical solution temperature (LCST). Cloud point curves of five polydisperse samples (Mw . 10-6 = 0.06 to 2.04) in aqueous solutions at concentrations from 0.002 to 0.1 g/ml were obtained. The threshold concentration was found to be almost independent of the molecular weight. The threshold temperature decreases moderately with increasing M and the limiting value for infinite M obtained by the Shultz-Flory method is ΘLPE = 340.5 K. This value is lower by 2.5 K than the temperature ΘLη at which the intrinsic viscosity is proportional to the square root of the molecular weight. The difference cannot be assigned to experimental errors. The entropy-of-dilution parameter is negative (ψ = -2) and much higher than the value obtained from dilute solution properties. The differences in Θ and ψ values are discussed in terms of theory of polymer solutions where a higher-order interaction parameter is included.

scholarly journals Synthesis, Structure, Hydrodynamics and Thermoresponsiveness of Graft Copolymer with Aromatic Polyester Backbone at Poly(2-isopropyl-2-oxazoline) Side Chains

Polymers ◽  
2020 ◽  
Vol 12 (11) ◽  
pp. 2643 ◽  
Author(s):  
Elena Tarabukina ◽  
Emil Fatullaev ◽  
Anna Krasova ◽  
Mikhail Kurlykin ◽  
Andrey Tenkovtsev ◽  
...  
Keyword(s):  
Aqueous Solutions ◽  
Graft Copolymer ◽  
Graft Copolymers ◽  
Linear Chain ◽  
Terminal Group ◽  
Solution Temperature ◽  
Side Chains ◽  
Critical Solution Temperature ◽  
Copolymer Solution ◽  
Aromatic Polyester

New thermoresponsive graft copolymers with an aromatic polyester backbone and poly(2-isopropyl-2-oxazoline) (PiPrOx) side chains are synthesized and characterized by NMR and GPC. The grafting density of side chains is 0.49. The molar masses of the graft-copolymer, its backbone, side chains, and the modeling poly-2-isopropyl-2-oxaziline are 74,000, 19,000, 4300, and 16,600 g·mol−1, respectively. Their conformational properties in nitropropane as well as thermoresponsiveness in aqueous solutions are studied and compared with that of free side chains, i.e., linear PiPrOx with a hydrophobic terminal group. In nitropropane, the graft-copolymer adopts conformation of a 13-arm star with a core of a collapsed main chain and a PiPrOx corona. Similarly, a linear PiPrOx chain protects its bulky terminal group by wrapping around it in a selective solvent. In aqueous solutions at low temperatures, graft copolymers form aggregates due to interaction of hydrophobic backbones, which contrasts to molecular solutions of the model linear PiPrOx. The lower critical solution temperature (LCST) for the graft copolymer is around 20 °C. The phase separation temperatures of the copolymer solution were lower than that of the linear chain counterpart, decreasing with concentration for both polymers.

scholarly journals How to manipulate the upper critical solution temperature (UCST)?

2017 ◽  
Vol 8 (1) ◽  
pp. 220-232 ◽  
Author(s):  
Jukka Niskanen ◽  
Heikki Tenhu
Keyword(s):  
Aqueous Solutions ◽  
Solution Temperature ◽  
Stimuli Responsive ◽  
Critical Solution Temperature ◽  
Stimuli Responsive Polymers ◽  
Responsive Polymers ◽  
Ph Influence ◽  
Counter Ions ◽  
Upper Critical Solution Temperature

In this mini-review, we discuss multi-stimuli-responsive polymers, which exhibit upper critical solution temperature (UCST) behavior mainly in aqueous solutions, and focus on examples where counter ions, electricity, light, or pH influence the thermoresponsiveness of these polymers.

scholarly journals Synthesis and characterization of temperature-sensitive and biodegradable hydrogel based on N-isopropylacrylamide

2010 ◽  
Vol 8 (2) ◽  
pp. 426-433 ◽  
Author(s):  
Yueqin Yu ◽  
Yanshun Li ◽  
Chunjing Zhu ◽  
Lingxiu Liu
Keyword(s):  
Enzymatic Degradation ◽  
Molar Ratio ◽  
Solution Temperature ◽  
Swelling Kinetics ◽  
Swelling Ratio ◽  
Nacl Solution ◽  
Equilibrium Swelling ◽  
Cross Linker ◽  
The Cross ◽  
Equilibrium Swelling Ratio

AbstractBased on a biodegradable cross-linker, N-maleyl chitosan (N-MACH), a series of Poly(N-isopropylacrylamide) (PNIPAAm) and Poly(N-isopropylacrylamide-co-acrylamide) [P(NIPAAm-co-Am)] hydrogels were prepared, and their lower critical solution temperature (LCST), swelling kinetics, equilibrium swelling ratio in NaCl solution, and enzymatic degradation behavior in simulated gastric fluids (SGF) were discussed. The LCST did not change with different cross-linker contents. By altering the NIPAAm/Am molar ratio of P(NIPAAm-co-Am) hydrogels, the LCST could be increased to 39°C. The LCST of the hydrogel was significantly influenced by the monomer ratio of the NIPAAm/Am but not by the cross-linker content. In the swelling kinetics, all the dry hydrogels exhibited fast swelling behavior, and the swelling ratios were influenced by the cross-linker content and NIPAAm/Am molar ratios. Equilibrium swelling ratio of all the hydrogels decreased with increasing NaCl solution concentration. In enzymatic degradation tests, the weight loss of hydrogels was dependent on the cross-linker contents and the enzyme concentration.

scholarly journals Phase Diagrams of Smart Copolymers Poly(N-isopropylacrylamide) and Poly(sodium acrylate)

2014 ◽  
Vol 2014 ◽  
pp. 1-8 ◽  
Author(s):  
Iwona Zarzyka ◽  
Maria Laura Di Lorenzo ◽  
Marek Pyda
Keyword(s):  
Water System ◽  
Solution Temperature ◽  
Sodium Acrylate ◽  
Linear Polymers ◽  
Scanning Calorimetry ◽  
Modulated Differential Scanning Calorimetry ◽  
Critical Solution Temperature ◽  
Mixing Behavior ◽  
Linear Poly ◽  
Copolymer Poly

The phase behavior of linear poly(N-isopropylacrylamide) (PNIPA), linear copolymer poly(N-isopropylacrylamide) and poly(sodium acrylate) (PNIPA-SA), and chemically cross-linked PNIPA in water has been determined by temperature modulated differential scanning calorimetry (TM-DSC). Experiments related to linear polymers (PNIPA and PNIPA-SA) indicated nontypical demixing/mixing behavior with a lower critical solution temperature (LCST), which do not correspond to the three classical types of limiting critical behavior. Some similarities and differences are observed in comparison to our literature data using standard TM-DSC for PNIPA/water. Furthermore no influence of composition cross-linked PNIPA/water system on demixing/mixing temperature was observed.

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