Probing the thermal collapse of PNIPAM grafts by quantitative in situ ellipsometry

2013 ◽  
Vol 1544 ◽  
Author(s):  
E.S. Kooij ◽  
X.F. Sui ◽  
M.A. Hempenius ◽  
H.J.W. Zandvliet ◽  
G.J. Vancso
Keyword(s):  
Density Profile ◽  
Spectroscopic Ellipsometry ◽  
Quantitative Description ◽  
Solution Temperature ◽  
Thickness Variation ◽  
Dense Layer ◽  
Chain Segment ◽  
Critical Solution Temperature ◽  
Gradient Density

ABSTRACTWe demonstrate the potential of spectroscopic ellipsometry for the investigation of the chain segment density profile and layer thickness during the temperature-induced, reversible collapse−expansion transition of poly(N-isopropylacrylamide) (PNIPAM) grafted layers with variable grafting densities in aqueous systems. To obtain a quantitative description of the thickness of our swollen PNIPAM layers, various models were implemented to fit the ellipsometric data. From the ellipsometry results, the density and thickness variation accompanying the collapse transition across the lower critical solution temperature (LCST) was characterized. The collapse can be adequately explained by considering the PNIPAM film to consist of two layers: (i) a dense layer near the surface and (ii) a more diluted layer with a gradient density profile on the side of the film exposed to the solvent.

Phase-separation immunoassays.

1987 ◽  
Vol 33 (9) ◽  
pp. 1509-1516 ◽  
Author(s):  
K Auditore-Hargreaves ◽  
R L Houghton ◽  
N Monji ◽  
J H Priest ◽  
A S Hoffman ◽  
...  
Keyword(s):  
Reaction Kinetics ◽  
Solid Phase ◽  
Specific Binding ◽  
Hepatitis B Surface Antigen ◽  
Solution Temperature ◽  
Critical Solution Temperature ◽  
Binding Reaction ◽  
Insoluble Polymer ◽  
Capture Antibody

Abstract Solid-phase-based immunoassays have traditionally been plagued by nonspecific binding to the solid phase and by slow reaction kinetics relative to reactants that are free to diffuse in solution. We have developed two novel immunoassays in which the solid phase is generated in situ after the specific binding reaction has occurred, thereby enhancing reaction kinetics and minimizing the opportunities for non-specific binding. In the first system, the capture antibody is conjugated to an organic monomer, polymerization of which to form insoluble polymer particles is initiated by a reaction involving free radicals. The amount of signal-labeled antibody incorporated into the resulting particles is directly proportional to the concentration of antigen. The principle is illustrated for the simultaneous assay of IgG and IgM in a single sample. In the second system, capture antibody is conjugated to a polymer, the solubility of which is a function of temperature. Specific binding is conducted below the critical solution temperature of the polymer, which is then separated from solution by increasing the temperature above the critical temperature. The incorporation of signal-labeled antibody into the precipitated polymer is directly proportional to the concentration of antigen. This principle is illustrated for the assay of hepatitis B surface antigen and Chlamydia trachomatis.

N-isopropylacrylamide-based Copolymers with Time-dependent LCST for a Bioresorbable Carrier

2004 ◽  
Vol 845 ◽  
Author(s):  
Bae Hoon Lee ◽  
Brent Vernon
Keyword(s):  
Body Temperature ◽  
Time Dependent ◽  
Solution Temperature ◽  
Gelation Temperature ◽  
Critical Solution Temperature ◽  
New Class ◽  
Polymeric Biomaterials ◽  
Localized Delivery ◽  
Hydrolysis Of

ABSTRACTTo develop a new class of in situ-forming, injectable, and biodegradable polymeric biomaterials based on time-dependent lower critical solution temperature (LCST) properties for localized delivery, copolymers of N-isopropylacrylamide (NIPAAm), 2-hydroxyethyl methacryl lactate (HEMA-lactate) and acrylic acid (AAc) were prepared with varying mole ratios of monomers. The copolymers showed LCST and gelation properties below body temperature in 0.1 N PBS solution of pH 7.4. The LCST and gelation temperature of the copolymers decreased as the HEMA-lactate content of the copolymers was increased. The copolymers also showed time-dependent LCST and gelation properties in 0.1 N PBS solution of pH 7.4 owing to hydrolysis of HEMA-lactate. Hydrolysis of HEMA-lactate caused the polymers to be more hydrophilic, resulting in an increase in LCST and gelation temperature. All the polymers with about 6 mol % AAc exhibited LCST and gelation temperature above body temperature after complete hydrolysis of HEMA-lactate.

scholarly journals Thermo-responsive super porous p(NIPAM) cryogels affords enhanced thermal stability and activity for ɑ-Glucosidase enzyme by entrapping in situ

2021 ◽  
Author(s):  
Sahin Demirci ◽  
Nurettin Sahiner
Keyword(s):  
Enzyme Immobilization ◽  
Storage Stability ◽  
Storage Conditions ◽  
Solution Temperature ◽  
Critical Solution Temperature ◽  
Enzyme Functionality ◽  
And Storage ◽  
Enzyme Entrapment ◽  
Temperature Storage

The concept of using a thermo-responsive p(NIPAM) polymer matrix for enzyme immobilization with lower critical solution temperature (LCST) value is rationalized by availability of the compartmental milieu to enzymes to operate within super porous 3-D matrix with special environmental conditions. Therefore, the enzyme immobilization within a support material will be carried out under the storage conditions of enzymes, generally ~-20 oC to afford unnecessarily loss of enzyme functionality in comparison to the other enzyme entrapment methods. Thus, here ɑ-Glucosidase as a model enzyme was entrapped within thermo-responsive super porous p(NIPAM) cryogels (ɑ-Glu@p(NIPAM) during the synthesis that uses cryogenic condition, ~-20 oC. The LSCT value for the prepared p(NIPAM) based cryogels were determined as 34.6±1.2 oC. The immobilization yield, immobilization efficiency, and activity recovery% values were calculated as 89.4±3.1, 66.2±3.3, and 74.0±3.3%, respectively at pH 6.8 and 37 oC for ɑ-Glu@p(NIPAM) cryogel system. Interestingly, the optimum working conditions were achieved as 25 oC and pH 6.8 with higher activity, 98.4±0.2% for the prepared ɑ-Glu@p(NIPAM) cryogel system. The operational and storage stability studies revealed that the prepared ɑ-Glu@p(NIPAM) cryogel system possessed much better operational and storage stability than free ɑ-Glu enzyme e.g., more than 50% activity after 10th usage and 10-day room temperature storage time. Moreover, the kinetic parameters such as Km and Vmax of free-Glu enzyme and ɑ-Glu@p(NIPAM) cryogel system were calculated by non-linear Michaelis-Menten equation.

Polydopamine Nanoparticle for Poly(N-Isopropylacrylamide)-Based Nanocomposite Hydrogel with Good Free-Radical-Scavenging Property

2016 ◽  
Vol 848 ◽  
pp. 94-98 ◽  
Author(s):  
Shu Qiang Xiong ◽  
Yan Wang ◽  
Jing Zhu ◽  
Zu Ming Hu ◽  
Jun Rong Yu
Keyword(s):  
Free Radical ◽  
Radical Scavenging ◽  
Antioxidant Property ◽  
Solution Temperature ◽  
Scavenge Activity ◽  
Initial Reaction ◽  
Critical Solution Temperature ◽  
Nanocomposite Hydrogels ◽  
Isopropyl Acrylamide

Nanocomposite hydrogels (NC gels) consisting of poly (N-Isopropyl acrylamide) (pNIPAM)/polydopamine nanoparticles (PDAPs) were prepared by in-situ-free-radical polymerization of N-isopropyl acrylamide in the presence of modified PDAP in aqueous solution. The composition of the NC gels could be controlled directly by altering the composition of the initial reaction mixture. The lower critical solution temperature (LCST) of the NC gels were studied by DSC, and the LCST of both of pure pNIPAM hydrogel and NC gels was at 34°C. Besides, the NC gels showed superior antioxidant property, and the ability to scavenge activity of NC gel was up to 70% with the addition of 6 wt% modified PDAP into pNIPAM.

Systematic Study on the Remote Triggering of Thermo-Responsive Hydrogels Using RF Heating of Fe3O4 Nanoparticles

2015 ◽  
Vol 1718 ◽  
pp. 35-40 ◽  
Author(s):  
Daniel Denmark ◽  
Devajyoti Mukherjee ◽  
Janae Bradley ◽  
Sarath Witanachchi ◽  
Pritish Mukherjee
Keyword(s):  
Systematic Study ◽  
Ion Concentration ◽  
Solution Temperature ◽  
Rf Heating ◽  
Critical Solution Temperature ◽  
Responsive Polymers ◽  
Transmission Electron ◽  
Remote Triggering ◽  
Responsive Hydrogels

ABSTRACTIn this work, a systematic study on the factors that influence the lower critical solution temperature (LCST) of poly(N-isopropylacrylamide) (PNIPAM) solutions during remote radiofrequency (RF) heating, using Fe3O4 magnetic nanoparticles (MNPs) is reported. A series of PNIPAM solutions with varying concentrations of Fe3O4 MNPs were prepared and characterized using transmission electron microscopy and Raman spectroscopy. Preliminary studies showed the highest specific absorption rate (SAR) for 15 nm sized Fe3O4 MNPs, which monotonically decreased as the MNP sizes increased to 20-30 nm. In-situ transmission measurements were used to determine the LCST of PNIPAM under various aqueous concentrations with dispersed Fe3O4 MNPs. A systematic decrease in the LCST from 34 °C to 31 °C was observed as the concentration of PNIPAM was increased from 0.3 wt. % to 1.0 wt. %, keeping the concentration of Fe3O4 MNPs constant. On the other hand, varying the concentrations of the MNPs did not drastically affect the LCSTs of PNIPAM solutions. However, varying the ion concentration of the PNIPAM solutions by adding adjusted KOH pellets, showed a pronounced lowering of the LCST by 2-3 °C at all PNIPAM concentrations. The remote triggering of phase transitions in PNIPAM solutions by raising the temperature above the LCST using Fe3O4 MNPs as reported here is important in targeted drug-delivery applications using thermo-responsive polymers.

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)...

scholarly journals Thermo- and Photoresponsive Behaviors of Dual-Stimuli-Responsive Organogels Consisting of Homopolymers of Coumarin-Containing Methacrylate

Polymers ◽  
2021 ◽  
Vol 13 (3) ◽  
pp. 329
Author(s):  
Seidai Okada ◽  
Eriko Sato
Keyword(s):  
Functional Group ◽  
Solution Temperature ◽  
Stimuli Responsive ◽  
Critical Solution Temperature ◽  
Equilibrium Degree ◽  
Stimuli Responsive Polymers ◽  
Responsive Polymers ◽  
Dual Functional ◽  
Wide Range ◽  
Increasing Temperature

Coumarin-containing vinyl homopolymers, such as poly(7-methacryloyloxycoumarin) (P1a) and poly(7-(2′-methacryloyloxyethoxy)coumarin) (P1b), show a lower critical solution temperature (LCST) in chloroform, which can be controlled by the [2 + 2] photochemical cycloaddition of the coumarin moiety, and they are recognized as monofunctional dual-stimuli-responsive polymers. A single functional group of monofunctional dual-stimuli-responsive polymers responds to dual stimuli and can be introduced more uniformly and densely than those of dual-functional dual-stimuli-responsive polymers. In this study, considering a wide range of applications, organogels consisting of P1a and P1b, i.e., P1a-gel and P1b-gel, respectively, were synthesized, and their thermo- and photoresponsive behaviors in chloroform were investigated in detail. P1a-gel and P1b-gel in a swollen state (transparent) exhibited phase separation (turbid) through a temperature jump and reached a shrunken state (transparent), i.e., an equilibrium state, over time. Moreover, the equilibrium degree of swelling decreased non-linearly with increasing temperature. Furthermore, different thermoresponsive sites were photopatterned on the organogel through the photodimerization of the coumarin unit. The organogels consisting of homopolymers of coumarin-containing methacrylate exhibited unique thermo- and photoresponsivities and behaved as monofunctional dual-stimuli-responsive organogels.

scholarly journals Morphology and crystallization kinetics of Rubber-modified Nylon 6 Prepared by Anionic In-situ Polymerization

2020 ◽  
Vol 27 (1) ◽  
pp. 204-215
Author(s):  
Hongkai Zhao ◽  
Dengchao Zhang ◽  
Yingshuang Li
Keyword(s):  
Crystallization Kinetics ◽  
In Situ Polymerization ◽  
Good Description ◽  
Nylon 6 ◽  
Avrami Equation ◽  
Infrared Analysis ◽  
Chain Segment ◽  
The Impact ◽  
Kinetics Of

AbstractIn this work, we modified nylon 6 with liquid rubber by in-situ polymerization. The infrared analysis suggested that HDI urea diketone is successfully blocked by caprolactam after grafting on hydroxyl of HTPB, and the rubber-modified nylon copolymer is generated by the anionic polymerization. The impact section analysis indicated the rubber-modified nylon 6 resin exhibited an alpha crystal form.With an increase in the rubber content, nylon 6 was more likely to generate stable α crystal. Avrami equation was a good description of the non-isothermal crystallization kinetics of nylon-6 and rubber-modified nylon-6 resin. Moreover, it is found that the initial crystallization temperature of nylon-6 chain segment decreased due to the flexible rubber chain segment. n value of rubber-modified nylon-6 indicated that its growth was the coexistence of two-dimensional discoid and three-dimensional spherulite growth. Finally, the addition of the rubber accelerated the crystallization rate of nylon 6.

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