Poly(N-isopropylacrylamide)

Last updated

Contents

Poly(N-isopropylacrylamide)
PNIPA.png
Identifiers
ChemSpider
  • none
PubChem CID
Properties [1]
(C6H11NO)n
Molar mass variable
Appearancewhite solid
Density 1.1 g/cm3
Melting point 96 °C (205 °F; 369 K)
Hazards [1]
NFPA 704 (fire diamond)
NFPA 704.svgHealth 0: Exposure under fire conditions would offer no hazard beyond that of ordinary combustible material. E.g. sodium chlorideFlammability 0: Will not burn. E.g. waterInstability 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no code
0
0
0
Safety data sheet (SDS) External MSDS
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

Poly(N-isopropylacrylamide) (variously abbreviated PNIPA, PNIPAM, PNIPAAm, NIPA, PNIPAA or PNIPAm) is a temperature-responsive polymer that was first synthesized in the 1950s. [2] It can be synthesized from N-isopropylacrylamide which is commercially available. It is synthesized via free-radical polymerization and is readily functionalized making it useful in a variety of applications.

PNIPA dissolves in water, however, when these solutions are heated in above their cloud point temperature, they undergo a reversible lower critical solution temperature (LCST) phase transition from a soluble hydrated state to an insoluble dehydrated state. Although it is widely believed that this phase transition occurs at 32 °C (90 °F), [3] the actual temperatures may differ 5 to 10 °C (or even more) depending on the polymer concentration, [3] molar mass of polymer chains, polymer dispersity as well as terminal moieties. [3] [4] Furthermore, other molecules in the polymer solution, such as salts or proteins, can alter the cloud point temperature. [5] [6]

Since PNIPA expels its liquid contents at a temperature near that of the human body, PNIPA copolymers have been investigated by many researchers for possible applications in tissue engineering [7] [8] and controlled drug delivery. [9] [10] [11] [12]

History

The synthesis of poly(N-isopropylacrylamide) began with the synthesis of the acrylamide monomer by Sprecht in 1956. [13] In 1957, Shearer patented the first application for what would be later identified as PNIPA for the use as a rodent repellent. [14] Early work was piqued by theoretical curiosity of the material properties of PNIPA. The first report of PNIPA came in 1968, which elucidated the unique thermal behavior in aqueous solutions. [15] The 1980s marked an explosion in interest in PNIPAs with the realization of potential applications due to its unique thermal behavior in aqueous solutions. [2]

Chemical and Physical Properties

PNIPA is one of the most studied thermosensitive hydrogels. In dilute solution, it undergoes a coil-to-globule transition. [16] PNIPA possesses an inverse solubility upon heating. It changes hydrophilicity and hydrophobicity abruptly at its LCST. [17] At lower temperatures PNIPA orders itself in solution in order to hydrogen bond with the already arranged water molecules. The water molecules must reorient around the nonpolar regions of PNIPA which results in a decreased entropy. At lower temperatures, such as room temperature, the negative enthalpy term () from hydrogen bonding effects dominates the Gibbs free energy,

causing the PNIPA to absorb water and dissolve in solution. At higher temperatures, the entropy term () dominates, causing the PNIPA to release water and phase separate which can be seen in the following demonstration.

A demonstration of the heating of PNIPA to demonstrate the LCST effect.

Synthesis of Heat and pH Sensitive PNIPA

Homopolymerization [18]

The process of free radical polymerization of a single type of monomer, in this case, N-isopropylacrylamide, to form the polymer is known as a homopolymerization. The radical initiator azobisisobutyronitrile (AIBN) is commonly used in radical polymerizations.
Homopolymerization of PNIPA.png

Copolymerization

A free-radical polymerization of two different monomer results in a copolymerization. An advantage to a copolymerization includes fine tuning of the LCST.
Copolymerization Synthesis of PNIPA.png

Terpolymerization

A free-radical polymerization of three different monomer is known as a terpolymerization. Advantages to a terpolymerization may include enhancing multiple properties of the polymer including thermosensitivity, pH sensitivity or fine tuning of the LCST.
Terpolymerization Synthesis of PNIPA.png

Cross-linked Hydrogel

The reaction scheme below is a terpolymerization to form a cross-linked hydrogel. The reactant ammonium persulfate (APS) is used in polymer chemistry as a strong oxidizing agent that is often used along with tetramethylethylenediamine (TMEDA) to catalyze the polymerization when making polyacrylamide gels.
Crosslinked Hydrogel Polymerization of PNIPA.png

Synthesis of Chain-End Functionalized PNIPA

PNIPA can be functionalized using chain transfer agents using a free radical polymerization. The three schemes below demonstrate functionalization using chain transfer agents (CTA), where one end of the polymer is the radical initiator and the other is a functionalized group. Functionalization of the polymer chain-end allows for the polymer to be used in many diverse settings and applications. Advantages to a functionalizing the chain-end may include enhancing multiple properties of the polymer including thermosensitivity, pH sensitivity or fine tuning of the LCST. [18]

(1) Functionalization CTA Scheme 1 of PNIPA.png

(2) Functionalization CTA Scheme 2 of PNIPA png.png

(3) Functionalization CTA Scheme 3 of PNIPA png.png

Applications

The versatility of PNIPA has led to finding uses in macroscopic gels, microgels, [19] membranes, sensors, biosensors, thin films, [20] [21] [22] tissue engineering, and drug delivery. The tendency of aqueous solutions of PNIPA to increase in viscosity in the presence of hydrophobic molecules has made it excellent for tertiary oil recovery.

As aqueous solutions of PNIPA have their lower critical solution temperature in temperatures around human body temperatures, these polymers can be dissolved in water at room temperature and administered into body. [23] However, upon the administration, these polymers phase-separate and form insoluble aggregates at site of administration (this process is called thermogelling). [23] When PNIPA is administered into muscles of mice, its half-life was approximately 48 days (Mw = 20 kg/mol) and 66 days (Mw = 32 kg/mol) and caused no local or systemic pathologies. [23] Such phase separated hydrogels can be used for local drug delivery applications. [24] The PNIPA can be placed in a solution of bioactive molecules, which allows the bioactive molecules to penetrate the PNIPA. The PNIPA can then be placed in vivo, where there is a rapid release of biomolecules due to the initial gel collapse and an ejection of the biomolecules into the surrounding media, followed by a slow release of biomolecules due to surface pore closure. [25]

PNIPA have also been used in pH-sensitive drug delivery systems. Some examples of these drug delivery systems may include the intestinal delivery of human calcitonin, [26] delivery of insulin, [26] and the delivery of ibuprofen. [27] When radiolabeled PNIPA copolymers with different molecular weights were intravenously injected to rats, it was found that the glomerular filtration threshold of the polymer was around 32 000 g/mol. [28]

PNIPA have been used in gel actuators, which convert external stimuli into mechanical motion. [29] Upon heating above the LCST, the hydrogel goes from hydrophilic to hydrophobic state. [30] This conversion results in an expulsion of water which causes a physical conformational change, creating a mechanical hinge movement.

Furthermore, PNIPA-based thin films can be applied as nano-switches featuring multiple distinct thin-film states, which is based on the cononsolvency effect. [31] [32] [33]

Related Research Articles

<span class="mw-page-title-main">Hydrogel</span> Soft water-rich polymer gel

A hydrogel is a biphasic material, a mixture of porous, permeable solids and at least 10% by weight or volume of interstitial fluid composed completely or mainly by water. In hydrogels the porous permeable solid is a water insoluble three dimensional network of natural or synthetic polymers and a fluid, having absorbed a large amount of water or biological fluids. These properties underpin several applications, especially in the biomedical area. Many hydrogels are synthetic, but some are derived from nature. The term 'hydrogel' was coined in 1894.

<span class="mw-page-title-main">Polyphosphazene</span>

Polyphosphazenes include a wide range of hybrid inorganic-organic polymers with a number of different skeletal architectures with the backbone P-N-P-N-P-N-. In nearly all of these materials two organic side groups are attached to each phosphorus center. Linear polymers have the formula (N=PR1R2)n, where R1 and R2 are organic (see graphic). Other architectures are cyclolinear and cyclomatrix polymers in which small phosphazene rings are connected together by organic chain units. Other architectures are available, such as block copolymer, star, dendritic, or comb-type structures. More than 700 different polyphosphazenes are known, with different side groups (R) and different molecular architectures. Many of these polymers were first synthesized and studied in the research group of Harry R. Allcock.

Poloxamers are nonionic triblock copolymers composed of a central hydrophobic chain of polyoxypropylene flanked by two hydrophilic chains of polyoxyethylene. The word poloxamer was coined by BASF inventor, Irving Schmolka, who received the patent for these materials in 1973. Poloxamers are also known by the trade names Pluronic, Kolliphor, and Synperonic.

Small-angle X-ray scattering (SAXS) is a small-angle scattering technique by which nanoscale density differences in a sample can be quantified. This means that it can determine nanoparticle size distributions, resolve the size and shape of (monodisperse) macromolecules, determine pore sizes, characteristic distances of partially ordered materials, and much more. This is achieved by analyzing the elastic scattering behaviour of X-rays when travelling through the material, recording their scattering at small angles. It belongs to the family of small-angle scattering (SAS) techniques along with small-angle neutron scattering, and is typically done using hard X-rays with a wavelength of 0.07 – 0.2 nm. Depending on the angular range in which a clear scattering signal can be recorded, SAXS is capable of delivering structural information of dimensions between 1 and 100 nm, and of repeat distances in partially ordered systems of up to 150 nm. USAXS can resolve even larger dimensions, as the smaller the recorded angle, the larger the object dimensions that are probed.

<span class="mw-page-title-main">Polyacrylic acid</span> Anionic polyelectrolyte polymer

Poly(acrylic acid) (PAA; trade name Carbomer) is a polymer with the formula (CH2-CHCO2H)n. It is a derivative of acrylic acid (CH2=CHCO2H). In addition to the homopolymers, a variety of copolymers and crosslinked polymers, and partially deprotonated derivatives thereof are known and of commercial value. In a water solution at neutral pH, PAA is an anionic polymer, i.e., many of the side chains of PAA lose their protons and acquire a negative charge. Partially or wholly deprotonated PAAs are polyelectrolytes, with the ability to absorb and retain water and swell to many times their original volume. These properties – acid-base and water-attracting – are the bases of many applications.

<span class="mw-page-title-main">Temperature-responsive polymer</span> Polymer showing drastic changes in physical properties with temperature

Temperature-responsive polymers or thermoresponsive polymers are polymers that exhibit drastic and discontinuous changes in their physical properties with temperature. The term is commonly used when the property concerned is solubility in a given solvent, but it may also be used when other properties are affected. Thermoresponsive polymers belong to the class of stimuli-responsive materials, in contrast to temperature-sensitive materials, which change their properties continuously with environmental conditions. In a stricter sense, thermoresponsive polymers display a miscibility gap in their temperature-composition diagram. Depending on whether the miscibility gap is found at high or low temperatures, either an upper critical solution temperature (UCST) or a lower critical solution temperature (LCST) exists.

<span class="mw-page-title-main">Lower critical solution temperature</span> Critical temperature below which components of a mixture are miscible for all compositions

The lower critical solution temperature (LCST) or lower consolute temperature is the critical temperature below which the components of a mixture are miscible in all proportions. The word lower indicates that the LCST is a lower bound to a temperature interval of partial miscibility, or miscibility for certain compositions only.

<i>N</i>,<i>N</i>-Methylenebisacrylamide Chemical compound, polyacrylamide crosslinker

N,N′-Methylenebisacrylamide (MBAm or MBAA, colloquially "bis") is the organic compound with the formula CH2[NHC(O)CH=CH2]2. A colorless solid, this compound is a crosslinking agent in polyacrylamides, e.g., as used for SDS-PAGE.

A nanogel is a polymer-based, crosslinked hydrogel particle on the sub-micron scale. These complex networks of polymers present a unique opportunity in the field of drug delivery at the intersection of nanoparticles and hydrogel synthesis. Nanogels can be natural, synthetic, or a combination of the two and have a high degree of tunability in terms of their size, shape, surface functionalization, and degradation mechanisms. Given these inherent characteristics in addition to their biocompatibility and capacity to encapsulate small drugs and molecules, nanogels are a promising strategy to treat disease and dysfunction by serving as delivery vehicles capable of navigating across challenging physiological barriers within the body. 

<span class="mw-page-title-main">2-Acrylamido-2-methylpropane sulfonic acid</span> Chemical compound

2-Acrylamido-2-methylpropane sulfonic acid (AMPS) was a Trademark name by The Lubrizol Corporation. It is a reactive, hydrophilic, sulfonic acid acrylic monomer used to alter the chemical properties of wide variety of anionic polymers. In the 1970s, the earliest patents using this monomer were filed for acrylic fiber manufacturing. Today, there are over several thousands patents and publications involving use of AMPS in many areas including water treatment, oil field, construction chemicals, hydrogels for medical applications, personal care products, emulsion coatings, adhesives, and rheology modifiers.

<span class="mw-page-title-main">Poly(methacrylic acid)</span> Chemical compound

Poly(methacrylic acid) (PMAA) is a polymer made from methacrylic acid (preferred IUPAC name, 2-methylprop-2-enoic acid), which is a carboxylic acid. It is often available as its sodium salt, poly(methacrylic acid) sodium salt. The monomer is a viscous liquid with a pungent odour. The first polymeric form of methacrylic acid was described in 1880 by Engelhorn and Fittig. The use of high purity monomers is required for proper polymerization conditions and therefore it is necessary to remove any inhibitors by extraction (phenolic inhibitors) or via distillation. To prevent inhibition by dissolved oxygen, monomers should be carefully degassed prior to the start of the polymerization.

Thermoresponsive polymers can be used as stationary phase in liquid chromatography. Here, the polarity of the stationary phase can be varied by temperature changes, altering the power of separation without changing the column or solvent composition. Thermally related benefits of gas chromatography can now be applied to classes of compounds that are restricted to liquid chromatography due to their thermolability. In place of solvent gradient elution, thermoresponsive polymers allow the use of temperature gradients under purely aqueous isocratic conditions. The versatility of the system is controlled not only through changing temperature, but through the addition of modifying moieties that allow for a choice of enhanced hydrophobic interaction, or by introducing the prospect of electrostatic interaction. These developments have already introduced major improvements to the fields of hydrophobic interaction chromatography, size exclusion chromatography, ion exchange chromatography, and affinity chromatography separations as well as pseudo-solid phase extractions.

<span class="mw-page-title-main">Graft polymer</span> Polymer with a backbone of one composite and random branches of another composite

In polymer chemistry, graft polymers are segmented copolymers with a linear backbone of one composite and randomly distributed branches of another composite. The picture labeled "graft polymer" shows how grafted chains of species B are covalently bonded to polymer species A. Although the side chains are structurally distinct from the main chain, the individual grafted chains may be homopolymers or copolymers. Graft polymers have been synthesized for many decades and are especially used as impact resistant materials, thermoplastic elastomers, compatibilizers, or emulsifiers for the preparation of stable blends or alloys. One of the better-known examples of a graft polymer is a component used in high impact polystyrene, consisting of a polystyrene backbone with polybutadiene grafted chains.

Timothy P. Lodge is an American polymer scientist.

Elastin-like polypeptides (ELPs) are synthetic biopolymers with potential applications in the fields of cancer therapy, tissue scaffolding, metal recovery, and protein purification. For cancer therapy, the addition of functional groups to ELPs can enable them to conjugate with cytotoxic drugs. Also, ELPs may be able to function as polymeric scaffolds, which promote tissue regeneration. This capacity of ELPs has been studied particularly in the context of bone growth. ELPs can also be engineered to recognize specific proteins in solution. The ability of ELPs to undergo morphological changes at certain temperatures enables specific proteins that are bound to the ELPs to be separated out from the rest of the solution via experimental techniques such as centrifugation.

Hydrogels are three-dimensional networks consisting of chemically or physically cross-linked hydrophilic polymers. The insoluble hydrophilic structures absorb polar wound exudates and allow oxygen diffusion at the wound bed to accelerate healing. Hydrogel dressings can be designed to prevent bacterial infection, retain moisture, promote optimum adhesion to tissues, and satisfy the basic requirements of biocompatibility. Hydrogel dressings can also be designed to respond to changes in the microenvironment at the wound bed. Hydrogel dressings should promote an appropriate microenvironment for angiogenesis, recruitment of fibroblasts, and cellular proliferation.

<span class="mw-page-title-main">Polysulfobetaine</span> Dipolar ion polymer

Polysulfobetaines are zwitterionic polymers that contain a positively charged quaternary ammonium and a negatively charged sulfonate group within one constitutional repeat unit. In recent years, polysulfobetaines have received increasing attention owing to their good biotolerance and ultralow-fouling behavior towards surfaces. These properties are mainly referred to a tightly bound hydration layer around each zwitterionic group, which effectively suppresses protein adsorption and thus, improves anti-fouling behavior. Therefore, polysulfobetaines have been typically employed as ultrafiltration membranes, blood-contacting devices, and drug delivery materials.

<span class="mw-page-title-main">Cononsolvency</span>

Cononsolvency is a phenomenon where two solvents that can typically readily dissolve a polymer, when mixed, at certain ratios of these two solvents, are no longer able to dissolve the polymer. This phenomenon is in contrast to cosolvency where two solvents that are both poor at dissolving a material, but when the two poor solvents admixed, can form a mixed solvent capable of dissolving the material.

Vitaliy Khutoryanskiy FRSC is a British and Kazakhstani scientist, a Professor of Formulation Science and a Royal Society Industry Fellow at the University of Reading. His research focuses on polymers, biomaterials, nanomaterials, drug delivery, and pharmaceutical sciences. Khutoryanskiy has published over 200 original research articles, book chapters, and reviews. His publications have attracted > 11000 citations and his current h-index is 50. He received several prestigious awards in recognition for his research in polymers, colloids and drug delivery as well as for contributions to research peer-review and mentoring of early career researchers. He holds several honorary professorship titles from different universities.

<span class="mw-page-title-main">Hydroxyethyl acrylate</span> Organic chemical-monomer

Hydroxyethyl acrylate is an organic chemical and a aliphatic compound. It has the formula C5H8O3 and the CAS Registry Number 818–61–1. It is REACH registered with an EU number of 212–454–9. It has dual functionality containing a polymerizable acrylic group and a terminal hydroxy group. It is used to make emulsion polymers along with other monomers and the resultant resins are used in coatings, sealants, adhesives and elastomers and other applications.

References

  1. 1 2 "Poly(N-isopropylacrylamide) Material Safety Data Sheet". sigmaadlrich.com. Retrieved January 24, 2014.
  2. 1 2 Schild, H.G. (1992). "Poly(N-isopropylacrylamide): Experiment, theory and application". Progress in Polymer Science. 17 (2): 163–249. doi:10.1016/0079-6700(92)90023-R.
  3. 1 2 3 Halperin A, Kröger M, Winnik FM (2015). "Poly(N-isopropylacrylamide) Phase Diagrams: Fifty Years of Research". Angew Chem Int Ed Engl. 54 (51): 15342–67. doi:10.1002/anie.201506663. PMID   26612195.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  4. ↑ Aseyev, Vladimir; Tenhu, Heikki; Winnik, Françoise M. (2010). "Non-ionic Thermoresponsive Polymers in Water". Advances in Polymer Science. Vol. 242. Berlin, Heidelberg: Springer Berlin Heidelberg. pp. 29–89. doi:10.1007/12_2010_57. ISBN   978-3-642-22296-2. ISSN   0065-3195.
  5. ↑ Kolouchová, Kristýna; Lobaz, Volodymyr; Beneš, Hynek; et al. (2021). "Thermoresponsive properties of polyacrylamides in physiological solutions". Polymer Chemistry. Royal Society of Chemistry (RSC). 12 (35): 5077–5084. doi: 10.1039/d1py00843a . hdl: 1854/LU-8724379 . ISSN   1759-9954. S2CID   238937814.
  6. ↑ Zhang, Yanjie; Furyk, Steven; Sagle, Laura B.; et al. (2007). "Effects of Hofmeister Anions on the LCST of PNIPAM as a Function of Molecular Weight†". The Journal of Physical Chemistry C. American Chemical Society (ACS). 111 (25): 8916–8924. doi:10.1021/jp0690603. ISSN   1932-7447. PMC   2553222 . PMID   18820735.
  7. ↑ von Recum, H. A.; Kikuchi, A.; Okuhara, M.; Sakurai, Y.; Okano, T.; Kim, S. W. (1998). "Retinal pigmented epithelium cultures on thermally responsive polymer porous substrates". Journal of Biomaterials Science, Polymer Edition. 9 (11): 1241–1253. doi:10.1163/156856298X00758. PMID   9860183.
  8. ↑ Lee, EL.; von Recum, HA (2010). "Cell culture platform with mechanical conditioning and nondamaging cellular detachment". J Biomed Mater Res A. 93 (2): 411–8. doi:10.1002/jbm.a.32754. PMID   20358641. S2CID   23022529.
  9. ↑ Chung, J. E.; Yokoyama, M.; Yamato, M.; et al. (1999). "Thermo-responsive drug delivery from polymeric micelles constructed using block copolymers of poly(N-isopropylacrylamide) and poly(butylmethacrylate)". Journal of Controlled Release. 62 (1–2): 115–127. doi:10.1016/S0168-3659(99)00029-2. PMID   10518643.
  10. ↑ Yan, Hu; Tsujii, Kaoru (2005). "Potential application of poly(N-isopropylacrylamide) gel containing polymeric micelles to drug delivery systems". Colloids and Surfaces B: Biointerfaces. 46 (3): 142–146. doi:10.1016/j.colsurfb.2005.10.007. hdl: 2115/1381 . PMID   16300934. S2CID   31084515.
  11. ↑ Filipe E. Antunes; Luigi Gentile; Lorena Tavano; Cesare Oliviero Rossi (2009). "Rheological characterization of the thermal gelation of poly(N-isopropylacrylamide) and poly(N-isopropylacrylamide)co-Acrylic Acid". Applied Rheology. doi:10.3933/ApplRheol-19-42064.
  12. ↑ Dang, Steven; Brady, John; Rel, Ryle; Surineni, Sreenidhi; O'Shaughnessy, Conor; McGorty, Ryan (August 2, 2021). "Core-shell droplets and microcapsules formed through liquid-liquid phase separation of a colloid-polymer mixture". arXiv.org. Retrieved March 17, 2024.
  13. ↑ US 2773063
  14. ↑ US 2790744
  15. ↑ M. Heskins; J. E. Guillet (1968). "Solution Properties of Poly(N-isopropylacrylamide)". Journal of Macromolecular Science, Part A. 2 (8): 1441–1455. doi:10.1080/10601326808051910.
  16. ↑ Wu, C; Wang, X (1998). "Globule-to-Coil Transition of a Single Homopolymer Chain in Solution" (PDF). Physical Review Letters. 80 (18): 4092–4094. Bibcode:1998PhRvL..80.4092W. doi:10.1103/PhysRevLett.80.4092. Archived from the original (PDF) on July 21, 2011. Retrieved September 25, 2010.
  17. ↑ Somasundaran, Ponisseril (2004). Encyclopedia of Surface and Colloid Science. Taylor & Francis. ISBN   978-0-8247-2154-1 . Retrieved February 13, 2014.
  18. 1 2 "Designing temperature and pH sensitive NIPAM based polymers". sigmaadlrich.com. Retrieved January 25, 2014.
  19. ↑ Widmann, Tobias; Kreuzer, Lucas P.; Hohn, Nuri; et al. (December 10, 2019). "Hydration and Solvent Exchange Induced Swelling and Deswelling of Homogeneous Poly(N-isopropylacrylamide) Microgel Thin Films". Langmuir. 35 (49): 16341–16352. doi:10.1021/acs.langmuir.9b03104. ISSN   0743-7463. PMID   31714092. S2CID   207940427.
  20. ↑ Kreuzer, Lucas P.; Widmann, Tobias; Hohn, Nuri; et al. (May 14, 2019). "Swelling and Exchange Behavior of Poly(sulfobetaine)-Based Block Copolymer Thin Films". Macromolecules. 52 (9): 3486–3498. Bibcode:2019MaMol..52.3486K. doi:10.1021/acs.macromol.9b00443. ISSN   0024-9297. S2CID   155174181.
  21. ↑ Kreuzer, Lucas P.; Widmann, Tobias; Bießmann, Lorenz; et al. (April 28, 2020). "Phase Transition Kinetics of Doubly Thermoresponsive Poly(sulfobetaine)-Based Diblock Copolymer Thin Films". Macromolecules. 53 (8): 2841–2855. Bibcode:2020MaMol..53.2841K. doi:10.1021/acs.macromol.0c00046. ISSN   0024-9297. S2CID   216346530.
  22. ↑ Kreuzer, Lucas P.; Widmann, Tobias; Aldosari, Nawarah; et al. (October 27, 2020). "Cyclic Water Storage Behavior of Doubly Thermoresponsive Poly(sulfobetaine)-Based Diblock Copolymer Thin Films". Macromolecules. 53 (20): 9108–9121. Bibcode:2020MaMol..53.9108K. doi:10.1021/acs.macromol.0c01335. ISSN   0024-9297. S2CID   226323489.
  23. 1 2 3 Groborz, Ondřej; Kolouchová, Kristýna; Pankrác, Jan; et al. (2022). "Pharmacokinetics of Intramuscularly Administered Thermoresponsive Polymers". Advanced Healthcare Materials. 11 (22). doi: 10.1002/adhm.202201344 . ISSN   2192-2640. PMID   36153823.
  24. ↑ A. T. Okano; Y. H. Bae; H. Jacobs; S. W. Kim (1990). "Thermally on-off switching polymers for drug permeation and release". Journal of Controlled Release. 11 (1–3): 255–265. doi:10.1016/0168-3659(90)90138-j.
  25. ↑ Allan S. Hoffman; Ali Afrassiabi; Liang Chang Dong (1986). "Thermally reversible hydrogels: II. Delivery and selective removal of substances from aqueous solutions". Journal of Controlled Release. 4 (3): 213–222. doi:10.1016/0168-3659(86)90005-2.
  26. 1 2 Schmaljohann, Dirk (2006). "Thermo- and pH-responsive polymers in drug delivery" (PDF). Advanced Drug Delivery Reviews. Elsevier. 58 (15): 1655–70. doi:10.1016/j.addr.2006.09.020. PMID   17125884 . Retrieved March 13, 2014.
  27. ↑ Zhu, Senmin; Zhou, Zhengyang; Zhang, Di (March 15, 2007). "Grafting of thermo-responsive polymer inside mesoporous silica with large pore size using ATRP and investigation of its use in drug release". J. Mater. Chem. 17 (23): 2428–2433. doi:10.1039/b618834f.
  28. ↑ Bertrand, N.; Fleischer, J.G.; Wasan, K.M.; et al. (2009). "Pharmacokinetics and biodistribution of N-isopropylacrylamide copolymers for the design of pH-sensitive liposomes". Biomaterials. 30 (13): 2598–2605. doi:10.1016/j.biomaterials.2008.12.082. PMID   19176241.
  29. ↑ Chandorkar, Yashoda; Castro Nava, Arturo; Schweizerhof, Sjören; et al. (September 6, 2019). "Cellular responses to beating hydrogels to investigate mechanotransduction". Nature Communications. Springer Science and Business Media LLC. 10 (1): 4027. Bibcode:2019NatCo..10.4027C. doi:10.1038/s41467-019-11475-4. ISSN   2041-1723. PMC   6731269 . PMID   31492837.
  30. ↑ Xiaobo Zhang; Cary L. Pint; Min Hyung Lee; et al. (2011). "Optically- and Thermally-Responsive Programmable Materials Based on Carbon Nanotube-Hydrogel Polymer Composites". Nano Letters. 11 (8): 3239–3244. Bibcode:2011NanoL..11.3239Z. doi:10.1021/nl201503e. PMID   21736337. S2CID   14317595.
  31. ↑ Kreuzer, Lucas P.; Geiger, Christina; Widmann, Tobias; et al. (August 10, 2021). "Solvation Behavior of Poly(sulfobetaine)-Based Diblock Copolymer Thin Films in Mixed Water/Methanol Vapors". Macromolecules. 54 (15): 7147–7159. Bibcode:2021MaMol..54.7147K. doi:10.1021/acs.macromol.1c01179. ISSN   0024-9297. S2CID   237724968.
  32. ↑ Kreuzer, Lucas P.; Lindenmeir, Christoph; Geiger, Christina; et al. (February 9, 2021). "Poly(sulfobetaine) versus Poly(N-isopropylmethacrylamide): Co-Nonsolvency-Type Behavior of Thin Films in a Water/Methanol Atmosphere". Macromolecules. 54 (3): 1548–1556. Bibcode:2021MaMol..54.1548K. doi:10.1021/acs.macromol.0c02281. ISSN   0024-9297. S2CID   234184714.
  33. ↑ Geiger, Christina; Reitenbach, Julija; Henschel, Cristiane; et al. (November 2021). "Ternary Nanoswitches Realized with Multiresponsive PMMA‐ b ‐PNIPMAM Films in Mixed Water/Acetone Vapor Atmospheres". Advanced Engineering Materials. 23 (11): 2100191. doi: 10.1002/adem.202100191 . ISSN   1438-1656. S2CID   235560292.
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.