Poly thermo-responsive polymer

Poly(7V-isopropylacrylamide) (PNlPAAm) is a well-known thermo-responsive polymer and exhibits a lower critical solution temperature (LCST) of 32°C in water. It assnmes a random coil structure (hydrophilic state) below the LCST and a collapsed globnlar stractnre (hydrophobic state) above. Because of this sharp reversible transition, this polymer finds a vast array of applications,... 

Thermo-responsive polymers have been used to release encapsulated drugs in response to temperature changes. These polymers typically undergo a rapid and reversible hydration-dehydration at lower critical solution temperature (LCST, from soluble to insoluble) or upper critical solution temperature (UCST, from insoluble to soluble) upon heating. [71] For example, a thermo-responsive polymer, poly (2-isopropyl- 2-oxazoline) (PiPrOx), was conjugated to pH-responsive poly(benzyl ether)dendrons, which exhibited sharp thermal transitions as well as pH-dependent behaviors (Fig. 4a).[105]... 

FIGURE 12.12 Schematic of mouse embryonic stem cells (mESC) attachment (above LCST) and detachment (below LCST) to/from thermo-responsive polymer substrates. Poly(ME02MA-co-OEGMA) polymer brushes are shown as chain extended at temperatures below the LCST forming a cell-resistant surface, whereas collapse of the bmshes above the LCST results in a more favorable surface for cell attachment [192]. 

It would be of interest to add some functionalities such as properties in response to changes in pH, temperature, electrical potential and so on as well as hydrophilic properties to PTFE surfaces by the combined technique just described. Poly(AT-isopropylaoylamide) (PNIPA ) is a well-known thermo-responsive polymer whose hydrogel undergoes a volume change around 31 C in an aqueous solution. And further, poly 2-(dimethylamino)ethyl methacrylate (PDMA) in a pH 10 buffer solution exhibits a drastic decrease in the transmittance around 28 °C, which is considered to come from a phase transition of PDMA chains (ii). Therefore, we have tried to prepare JV -isopropylacrylamide (NIPAAm) or 2-(dimethylamino)ethyl... 

CHR Christova, D., Velichkova, R., Loos, W., Goethals, E.J., and DirPrez, F., New thermo-responsive polymer materials based on poly(2-ethyl-2-oxazoline) segments. Polymer, 44, 2255, 2003. 

A-substituted acrylamides are an extensive class of thermo-responsive polymers that have attracted a lot of interest due to their unique thermo-responsive behavior in aqueous media. Among this class, poly(A -isopropylacrylamide) (PNIPAAm) is the most extensively studied polymer for structure activity relationships (Bae, Okano, Kim, 1990 Feil, Bae, Feijen, Kim, 1992) and potential thermo-responsive apphcations. 

Poly(A-vinylamides) are another class of synthetic thermo-responsive polymers. Two of the most common polymers of this class are poly(Al-vinylpyrrolidone) (PVP) and poly(A-vinylcaprolactam) (PVCL) (Figure 1.3). PVCL is a water-soluble nonionic amphiphilic polymer with its basic unit comprising a seven-membered cyclic amide with a polar hydrophilic carboxyl group and an amide group connected directly to a hydrophobic vinyl chain. 

Alaghemandi, M., Spohr, E. (2012). Molecular dynamics investigation of the thermo-responsive polymer poly(A-isopropylacrylamide). MacromolecularTheory and Simulations, 21,106-112. 

Another route towards biomolecular functionalisation of switchable cell culture carriers was proposed by Gramm et al. (2011). The thermo-responsive polymer poly (vinyl methyl ether) was blended with a small amount of the alternating copolymer of vinyl methyl ether and maleic anhydride. After electron beam cross-linking, stable films with a dry thickness of up to 70 nm were obtained. The introduced anhydride moieties allow for subsequent protein or peptide immobilization without toxic coupling agents. This concept was applied and further developed by Teich-mann et al. (2013). The impact of different adhesion-promoting molecules immobilised in different concentrations to the thermo-responsive coating was evaluated and compared. 

However, the development of in vivo applications for PNIPAM is limited by its non-biodegradability and the presence of amide moieties that reduce its biocompatibility. For this reason, other thermo-responsive polymers have been investigated in recent years. Poly(N-vinylcaprolactam) is a promising alternative. This polymer has a LCST between 35 and 38°C, again close to the temperature of the human body, and is characterized by high biocompatibility and low toxicity (Konak et al, 2007 Medeiros et al, 2010 Shtanko et al, 2003 Yanul et al, 2001). Additionally, amphiphilic copolymers such as Pluronics and Tetronics have been developed, based on copolymers of polyethylene oxide and polypropylene oxide. These copolymer systems exhibit a solution-gel transition at close to human body temperature that permits their application as injectable implants (Samchenko et ai,2011). 

In a previous study, our group synthesized a new temperature and pH-sensitive poly(2-(dimethylamino) ethylmethacrylate-fe-vinylcaprolactam-fc-(2-(dimethylamino) ethyl methacrylate)), PDMAEMA- i-PVCL-fc-PDMAEMA, triblock copolymer by RAFT polymerization. PDMAEMA is dual sensitive (pH and temperature) and its LCST was around 50 °C, while PVCL is a thermo-responsive polymer and its LCST was around 32 °C. By modifying the structure and adjusting the composition of these polymers it is possible reduce the LSCT and pK values in order to ensure compatibility with physiological temperature and pH (see Table 9.1, Triblock 1). The results showed that these polymers can self-assemble into micelles in different environments [60]. 

The most commonly studied thermo-responsive polymers are poly (N-isopropylacrylamide), poly(2-alkyl-2-oxazoline)s, poly(vinyl methyl ether), poly(N-vinyl caprolactam), and polymers of oligoethylene glycol (meth)acrylates. Each of them is characterized with specific LCST, mechanism of heat-driven phase transition, structure and properties of the resulting mesoglobules, as well as with varying extents of reversibility and reproducibility of the process of mesoglobule formation [58]. The most preferable characteristics of the thermo-responsive polymers and mesoglobules used as templates for nanocapsule preparation have been formulated below [58] ... 

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