scholarly journals Thermal Behaviour of Common Thermoresponsive Polymers in Phosphate Buffer and in Its Salt Solutions

Polymers ◽  
2020 ◽  
Vol 13 (1) ◽  
pp. 90
Author(s):  
Łukasz Otulakowski ◽  
Maciej Kasprów ◽  
Aleksandra Strzelecka ◽  
Andrzej Dworak ◽  
Barbara Trzebicka
Keyword(s):  
Thermal Behaviour ◽  
Phosphate Buffer ◽  
Pure Water ◽  
Thermal Response ◽  
The Body ◽  
Solution Temperature ◽  
Thermoresponsive Polymers ◽  
Aqueous Polymer ◽  
Cloud Point Temperature ◽  
Size Of Particles

Thermoresponsive polymers are a promising material for drug nanocarrier preparation, which makes the study of their aggregation in physiological conditions very important. In this paper, the thermal behaviour of the thermoresponsive polymers poly(N-isopropylacrylamide), poly(2-isopropyl-2-oxazoline-co-2-n-propyl-2-oxazoline) and poly[(2-hydroxyethyl methacrylate)-co-oligo(ethylene glycol) methyl ether methacrylate] were studied in phosphate buffer (PBS) and solutions of its salts in concentration as in PBS. The thermal response of the polymers was measured using UV-Vis and dynamic light scattering (DLS). The salts shifted the cloud point temperature (TCP) of the (co)polymers to higher values compared to the TCP of aqueous polymer solutions. In PBS and NaCl solutions, all polymers exhibited an unexpected and previously unreported transmittance profile. During heating, an additional aggregation of polymers appeared above the TCP accompanied by the formation of a precipitate. In monosodium phosphate solutions and pure water, the studied polymers showed lower critical solution temperature (LCST-type) behaviour. DLS measurements showed that a salt influenced the size of the resulting polymer particles. The sizes and stability of particles depended on the heating rate. In PBS and NaCl solutions, the size of particles in the dispersion decreased above 60 °C, and the precipitate appeared on the bottom of the cuvette. The additional aggregation of polymer and its falling out of solution may hinder the removal of carriers from the body and has to be taken into account when preparing nanocarriers.

scholarly journals In-operando study of swelling and switching of thermo-responsive polymer films

2014 ◽  
Vol 70 (a1) ◽  
pp. C1174-C1174
Author(s):  
Qi Zhong ◽  
Weinan Wang ◽  
Achille Bivigou-Koumba ◽  
Andre Laschewsky ◽  
Christine Papadakis ◽  
...  
Keyword(s):  
Thin Film ◽  
Film Thickness ◽  
The Body ◽  
Switching Behavior ◽  
Solution Temperature ◽  
Light Modulation ◽  
Thermoresponsive Polymers ◽  
Time Resolved ◽  
In Operando ◽  
Kinetics Of

Thermo-responsive polymers can exhibit a demixing transition which is of the lower critical solution temperature (LCST) type. The collapse transition of polymers with such LCST behavior is of great interest for applications where a strong change of volume is desired even for small changes of an external stimulus such as temperature. Examples of applications are valves in micro-fluidics, the release of drugs in the body or sensors. A polymer which is a promising candidate in this context is poly(N-isopropylacrylamide), PNIPAM. It exhibits a LCST of about 320C that is attributed to alterations in the hydrogen-bonding interactions of the amide group. A polymer with a higher transition temperature as compared to PNIPAM is the thermosensitive acrylate poly(methoxydiethylene glycol acrylate) or PMDEGA. In thin film geometry, such thermoresponsive polymers are of particular interest for use as thermosensitive surfaces, artificial pumps and muscles, light modulation systems and optical switches. The strong volume change translates into a change of the film thickness due to the thin film geometry. We investigate the kinetics of chain collapse of thin thermosensitive films as a function of quench depth. Homopolymer films and amphiphilic block copolymer films are compared. With time resolved neutron reflectivity (NR) we follow the kinetics of the transition from a swollen to a collapsed thermoresponsive film. Within 15 seconds a full NR curve is probed, which allows to determine the evolution of film thickness and of the water content in real time. Thus, we investigate in-operando the switching behavior caused by a thermal trigger. The observed complex three-step switching of the films is discussed.

scholarly journals Thermoresponsive Polymers of Poly(2-(N-alkylacrylamide)ethyl acetate)s

Polymers ◽  
2020 ◽  
Vol 12 (11) ◽  
pp. 2464
Author(s):  
Xue Liu ◽  
Yuwen Hou ◽  
Yimin Zhang ◽  
Wangqing Zhang
Keyword(s):  
Ethyl Acetate ◽  
Raft Polymerization ◽  
Polymer Concentration ◽  
Degree Of Polymerization ◽  
Random Copolymers ◽  
Solution Temperature ◽  
Thermoresponsive Polymers ◽  
Induction Periods ◽  
Alkyl Groups ◽  
Cloud Point Temperature

Thermoresponsive poly(2-(N-alkylacrylamide) ethyl acetate)s with different N-alkyl groups, including poly(2-(N-methylacrylamide) ethyl acetate) (PNMAAEA), poly(2-(N-ethylacrylamide) ethyl acetate) (PNEAAEA), and poly(2-(N-propylacrylamide) ethyl acetate) (PNPAAEA), as well as poly(N-acetoxylethylacrylamide) (PNAEAA), were synthesized by solution RAFT polymerization. Unexpectedly, it was found that there are induction periods in the RAFT polymerization of these monomers, and the induction time correlates with the length of the N-alkyl groups in the monomers and follows the order of NAEAA < NMAAEA < NEAAEA < NPAAEA. The solubility of poly(2-(N-alkylacrylamide) ethyl acetate)s in water is also firmly dependent on the length of the N-alkyl groups. PNPAAEA including the largest N-propyl group is insoluble in water, whereas PNMAAEA and PNEAAEA are thermoresponsive in water and undergo the reversible soluble-to-insoluble transition at a critical solution temperature. The cloud point temperature (Tcp) of the thermoresponsive polymers is in the order of PNEAAEA < PNAEAA < PNMAAEA. The parameters affecting the Tcp of thermoresponsive polymers, e.g., degree of polymerization (DP), polymer concentration, salt, urea, and phenol, are investigated. Thermoresponsive PNMAAEA-b-PNEAAEA block copolymer and PNMAAEA-co-PNEAAEA random copolymers with different PNMAAEA and/or PNEAAEA fractions are synthesized, and their thermoresponse is checked.

GALEN ON THE HYGIENE OF THE NEWBORN

PEDIATRICS ◽  
1973 ◽  
Vol 52 (6) ◽  
pp. 840-840
Author(s):  
T. E. C.
Keyword(s):  
Medical History ◽  
Newborn Infant ◽  
Pure Water ◽  
The Body ◽  
The Other ◽  
Asia Minor ◽  
Cold Air ◽  
Marcus Aurelius ◽  
Personal Physician ◽  
To Come

Claudius Galenus is one of the most remarkable figures in medical history. Born at Pergamos in Asia Minor, A.D. 131, he travelled extensively, studied medicine at Alexandria, and in 162 settled in Rome, where in 169 he became the personal physician to the Emperor Marcus Aurelius. In his text entitled Hygiene (De Sanitate Tuenda) he described the care of the newborn infant as follows: The newborn infant, in his entire constitution, should first be powdered moderately and wrapped in swaddling-clothes, in order that his skin may be made thicker and firmer than the parts within. For during pregnancy everything was equally soft, since nothing of a harder nature touched it from without, and no cold air came in contact with it, whereby the skin would be contracted and thickened, and would become tougher and denser than it was before and than the other parts of the body. But when the baby is born, it is necessarily going to come in contact with cold and heat and with many bodies harder than itself. Therefore it is appropriate that his natural covering should be best prepared by us for exposure. For infants who are in accordance with nature, a simple salt dusting-power is sufficient; for those whom it is necessary to sprinkle with dried leaves of myrrh, or something else of this sort, are obviously abnormal. But at present it is our purpose to discuss those of the best constitution. These, then, as has been said, having been wrapped in swaddling-clothes, should receive milk for nourishment, and baths of pure water; for they require a completely moist regime, since they have a moister constitution than those of other ages. . . .

scholarly journals Preparation and Properties of Thermoresponsive P(N-Isopropylacrylamide-co-butylacrylate) Hydrogel Materials for Smart Windows

2019 ◽  
Vol 2019 ◽  
pp. 1-7 ◽  
Author(s):  
Jae-Hyung Park ◽  
Ji-Won Jang ◽  
Jae-Hak Sim ◽  
Il-Jin Kim ◽  
Dong-Jin Lee ◽  
...  
Keyword(s):  
Light Transmission ◽  
Crosslinking Agent ◽  
Three Dimensional ◽  
Light Transmittance ◽  
Solar Light ◽  
Solution Temperature ◽  
Smart Window ◽  
Thermoresponsive Polymers ◽  
Smart Windows ◽  
Hydrogel Films

Thermoresponsive polymers that exhibit phase transition in response to temperature change can be used as material for smart windows because they can control solar light transmission depending on the outside temperature. The development of thermoresponsive polymers for a smart window that can be used over a wide temperature range is required. Therefore, to obtain smart window materials that can be used at various temperatures, three-dimensional thermoresponsive P(NIPAm-co-BA) hydrogels were prepared by free radical polymerization from main monomer N-isopropylacrylamide, comonomer butyl acrylate, and crosslinking agent N,N′-methylenebisacrylamide (MBAm) in this study. This study examined the effect of BA content on the lower critical solution temperature (LCST) and the solar light transmittance of crosslinked P(NIPAm-co-BA) hydrogel films. The LCST of hydrogel films was found to be significantly decreased from 34.3 to 29.5°C with increasing BA content from 0 to 20 mol%. It was found that the transparent films at T=25°C (T<LCST) were converted to translucent films at a higher temperature (T=45°C) (T>LCST). These results suggested that the crosslinked P(NIPAm-co-BA) hydrogel materials prepared in this study could have high potential for application in smart window materials.

Studies on natural convection-induced flow and thermal behaviour inside electronic equipment cabinet model

2003 ◽  
Vol 217 (3) ◽  
pp. 323-328 ◽  
Author(s):  
M Ishizuka ◽  
Y Kitamura
Keyword(s):  
Natural Convection ◽  
Thermal Behaviour ◽  
Stokes Equations ◽  
Three Dimensional ◽  
The Body ◽  
Electronic Equipment ◽  
Navier Stokes ◽  
Surface Boundary ◽  
Surface Boundary Layer ◽  
Induced Flow

In the present work, an important basic flow phenomenon, natural convection-induced flow, is studied numerically. Three-dimensional Navier-Stokes equations along with the energy equation are solved based on the finite difference method. A generalized coordinate system is used so that sufficient grid resolution could be achieved in the body surface boundary layer region. The results of calculation showed a satisfactory agreement with the measured data and led to a good understanding of the overall flow and thermal behaviour inside an electronic equipment cabinet model, which is very difficult, if not impossible, to gather by experiment.

Thermoresponsive polymers with lower critical solution temperature: from fundamental aspects and measuring techniques to recommended turbidimetry conditions

2017 ◽  
Vol 4 (2) ◽  
pp. 109-116 ◽  
Author(s):  
Qilu Zhang ◽  
Christine Weber ◽  
Ulrich S. Schubert ◽  
Richard Hoogenboom
Keyword(s):  
Lower Critical Solution Temperature ◽  
Temperature Behavior ◽  
Solution Temperature ◽  
Thermoresponsive Polymers ◽  
Critical Solution Temperature ◽  
Measuring Techniques

This focus article addresses fundamental and practical aspects of investigating polymers with lower critical solution temperature behavior.

scholarly journals Synthesis and characterization of thermoresponsive hydrogels cross-linked with chitosan

2008 ◽  
Vol 6 (1) ◽  
pp. 107-113 ◽  
Author(s):  
Yueqin Yu ◽  
Xianzhi Chang ◽  
Hansheng Ning ◽  
Shusheng Zhang
Keyword(s):  
Acrylic Acid ◽  
Pure Water ◽  
Solution Temperature ◽  
Feed Ratio ◽  
Cross Linking ◽  
Environmentally Responsive ◽  
Extracellular Materials ◽  
Degradation Properties ◽  
Phosphate Buffered Saline

AbstractHydrogels composed of N-isopropylacrylamide (NIPAAm) and acrylic acid (AAc) were prepared by redox polymerization with degradable chitosan cross-linkers. Chitosan degradable cross-linkers were synthesized by the acrylation of the amine groups of glucosamine units within chitosan and characterized with 1H NMR. With the chitosan cross-linkers, loosely cross-linked poly(N-isopropylacryamideco-acrylic acid) [P(NIPAAm-co-AAc)] hydrogels were prepared, and their phase transition behavior, lower critical solution temperature (LCST), water content and degradation properties were investigated. The chitosan cross-linked P(NIPAAm-co-AAc) hydrogels were pliable and transparent at room temperature. The LCST could be adjusted at 32∼39°C by alternating the feed ratio. Swelling was influenced by NIPAAm/AAc monomer ratio, cross-linking density, swelling media, and temperature. All hydrogels with different feeding ratios contained more than 95% water at 25°C in the ultra pure water and phosphate-buffered saline (PBS, pH = 7.4 ± 0.1), and had a prospective swelling in the simulated gastric fluids (SGF, pH = 1.2) &gt; 72.54%. In degradation studies, breakdown of the chitosan cross-linked P(NIPAAm-co-AAc) hydrogels was dependent on the cross-linking density. The chitosan cross-linked P(NIPAAm-co-AAc) hydrogels which can be tailored to create environmentally-responsive artificial extracellular materials have great potential for future use.

Stability and Cell Adhesion Properties of Poly(N-isopropylacrylamide) Brushes with Variable Grafting Densities

2011 ◽  
Vol 64 (9) ◽  
pp. 1261 ◽  
Author(s):  
Xiaofeng Sui ◽  
Andrea Di Luca ◽  
Michel Klein Gunnewiek ◽  
E. Stefan Kooij ◽  
Clemens A. van Blitterswijk ◽  
...  
Keyword(s):  
Cell Adhesion ◽  
Atom Transfer Radical Polymerization ◽  
Radical Polymerization ◽  
Lower Critical Solution Temperature ◽  
Polymer Brushes ◽  
Pure Water ◽  
Solution Temperature ◽  
Atom Transfer ◽  
Adhesion Properties ◽  
Critical Solution Temperature

Poly(N-isopropylacrylamide) brushes with three different grafting densities were synthesized via surface-initiated atom-transfer radical polymerization on glass or on silicon substrates. The substrates were modified with monochlorosilane-based or trimethoxysilane-based atom-transfer radical polymerization initiators. Atomic force microscopy images showed detachment of brushes from the monochlorosilane-based system under cell culture conditions. In situ ellipsometry demonstrated the reversible swelling and collapse of the brushes as the temperature was varied across the lower critical solution temperature of poly(N-isopropylacrylamide) in pure water. The polymer brushes were evaluated as supporting substrates for MC-3T3 cell cultures. At 37°C (T>lower critical solution temperature), the seeded cells adhered, spread, and proliferated, whereas at 25°C (T<lower critical solution temperature), the cells detached from the surface. The low-density polymer brush showed the highest cell adhesion, featuring adhering cells with an elongated morphology.

Homogeneous nucleation of gas bubbles in vivo

1982 ◽  
Vol 53 (4) ◽  
pp. 940-946 ◽  
Author(s):  
P. K. Weathersby ◽  
L. D. Homer ◽  
E. T. Flynn
Keyword(s):  
Homogeneous Nucleation ◽  
De Novo ◽  
Decompression Sickness ◽  
Biological Fluids ◽  
Pure Water ◽  
Gas Bubbles ◽  
The Body ◽  
Nucleation Theory ◽  
Two Parameters

Several current theories of decompression sickness (DCS) presume the preexistence of gas bubble nuclei in tissue, because the de novo nucleation of gas bubbles in the body is thought to be theoretically impossible. Reexamination of nucleation theory reveals the overwhelming importance of two parameters: gas supersaturation and tissue surface tension (gamma). For the high gamma of pure water nucleation theoretically requires more than 1,000 ATA supersaturation. Lower values of gamma allow nucleation to occur with vastly smaller supersaturations. Application of homogeneous nucleation theory can provide reasonable fits to both rat and human pressure-reduction data with values of gamma within the range reported for biological fluids (below 5 dyn/cm). The initial bubble sizes predicted are 0.1 micron or less. The presence of heterogeneous sites, for example crevices and lipid surfaces, makes nucleation even more likely.

THERMOSENSITIVE NANOPARTICLES CONJUGATING WITH CD34 ANTIBODY AND ITS SOLUTION PEROPERTIES

2006 ◽  
Vol 18 (05) ◽  
pp. 222-228 ◽  
Author(s):  
CHUN-TE TAO ◽  
TAI-HORNG YOUNG
Keyword(s):  
Controlled Release ◽  
Cloud Point ◽  
Lower Critical Solution Temperature ◽  
Homogeneous Solution ◽  
The Body ◽  
Solution Temperature ◽  
Temperature Sensitive ◽  
Critical Solution Temperature ◽  
Human Cd34 ◽  
Collapse Temperature

Poly N-isopropylacrylamide (PNIPAAm) is a well-known temperature-sensitive polymer. When the temperature is higher than the lower critical solution temperature (LCST), PNIPAAm aquous solution is cloudy (phase separation occurred). In contrast, when the temperature is lower than the LCST, PNIPAAm is soluble in water (a homogeneous solution). The lower critical solution temperature (LCST) in aqueous solution of PNIPAAm was about 32~33°C. We prepared nano-scaled PNIPAAm particles containing carboxylic group on their surfaces by introducing acrylic acid monomer. The carboxylic groups were applied to conjugate with the amino group of the CD34 antibody. This immuno-conjugate can be applied on targeting the human CD34 positive cells, peripheral blood progenitor cells included, for cell purification and drug controlled release. In order to the active responding of controlled release of the conjugate in the body influenced by temperature, we hope to estimate the shifting of the gel-collapse temperature or cloud point of the immuno-conjugates by dynamic light scattering (DLS) and UV absorption. The results show that the gel-collapse temperature of the nano-particle was not significantly affected by the content of AA between 1.5~5 mol%. However, cloud point of the solution was elevated by the conjugation of CD34 antibody to 37°C. When CD34-conjugated particle was subsequently incorporated with recombinant FLT3-ligand, which is a smaller molecule compare to CD34 antibody, cloud point of the solution was not affected.

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