Thermo‐Responsive PNIPAAm Copolymers with Hydrophobic Spacers

Stoica, F.; Miller, Aline F.; Alexander, Cameron; Saiani, Alberto

doi:10.1002/masy.200750505

Cited by 8 publications

(7 citation statements)

References 10 publications

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“…This is because, when the samples are heated to temperature above LCST, some additional intersegment hydrogen bonds are formed between the collapsed chains; thus, during cooling this chain, dissociation occurs only when the temperature is lower than the LCST. Similar observations have been made by several researchers on NIPAAm-based polymers; [22][23][24][25][26][27][28] Cheng et al 25 confirmed the presence of additional hydrogen bonds during polymer heating by FTIR analysis where the intensity for hydrogen bonding between polymer PHEMA and grafted P(HEMA-g-(NIPAAm-coAAm)) hydrogel synthesis PHEMA samples, which are solid and transparent, were successfully synthesized in the method discussed in the Experimental section. In the highly cross-linked PHEMA hydrogels, an increase in crosslinking density created samples that were more rigid and had lower swelling ratios.…”

Section: Oligomer Lcstssupporting

confidence: 76%

Development of a thermosensitive grafted drug delivery system—synthesis and characterization of NIPAAm‐based grafts and hydrogel structure

Ankareddi

Brazel

2010

J of Applied Polymer Sci

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A thermosensitive grafted hydrogel was investigated for heating-activated drug release. The hydrogel was created by grafting oligomers of N-isopropylacrylamide-co-acrylamide (AAm) to a poly(2-hydroxyethyl methacrylate), or PHEMA, hydrogel. N-Isopropylacrylamide-co-AAm oligomers were synthesized with a range of compositions to raise the lower critical solution temperature (LCST) above physiological temperature. PHEMA hydrogels with these thermosensitive grafts were synthesized by free-radical solution polymerization, using an acrylated version of the oligomers. The oligomers were characterized for their molecular weight, LCSTs, and rate of response to a change in temperature. With the flexibility in tuning their properties by varying reaction parameters, these oligomers present possibilities in several fields, including drug delivery. The impact of cross-linking agent type and the amount and presence of grafts on the polymer network structure was found by determining the hydrogel mesh sizes. PHEMA gels cross-linked with methylenebisacrylamide had larger mesh sizes than those crosslinked with ethylene glycol dimethacrylate. Increasing amounts of cross-linking agent decreased mesh sizes. LCSTs exhibited by oligomers were slightly lower than those exhibited by polymer gels of the same composition. The grafting reaction was found to have only a slight impact on the hydrogel mesh size.

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Section: Oligomer Lcstssupporting

confidence: 76%

Development of a thermosensitive grafted drug delivery system—synthesis and characterization of NIPAAm‐based grafts and hydrogel structure

Ankareddi

Brazel

2010

J of Applied Polymer Sci

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“…However, it is possible to modify the LCST of a thermosensitive hydrogel by introducing the appropriate monomer moieties. The bulk copolymerization of a main thermosensitive monomer and another comonomer that modulates the LCST of the resulting polymer has been extensively studied, − allowing the thermosensitive polymer to be engineered according to specific needs.…”

Section: Introductionmentioning

confidence: 99%

Tailoring the LCST of Thermosensitive Hydrogel Thin Films Deposited by iCVD

2014

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Using the iCVD (initiated chemical vapor deposition) polymerization technique, we generated a library of thermosensitive thin film hydrogels in the physiological temperature range. The library shows how a specific hydrogel with a desired temperature response can be synthesized via the copolymerization of three main components: (a) the main thermosensitive monomer, which determines the temperature range of the LCST; (b) the comonomer, which modulates the temperature according to its hydrophilic/hydrophobic behavior; and (c) the cross-linker, which determines the swelling degree and the polymer chain mobility of the resulting hydrogel. The thermosensitive thin films included in the library have been characterized by the water contact angle (WCA), revealing a switchable hydrophobic/hydrophilic behavior depending on the temperature and a decrease in the WCA with the incorporation of hydrophilic moieties. Moreover, a more accurate characterization by quartz crystal microbalance (QCM) is performed. With temperature and flow control, the switchable swelling properties of the thermosensitive thin films (due to the polymer mixture transition) can be recorded and analyzed in order to study the effects of the comonomer moieties on the lower critical solution temperature (LCST). Thus, the LCST tailoring method has been successfully used in this paper, and thermoresponsive thin films (50 nm in thickness) have been deposited by iCVD, exhibiting LCSTs in the 32-49 °C range. Due to the presented method's ability to tailor the LCST in the physiological temperature range, the developed thermoresponsive films present potential biosensing and drug delivery applications in the biomedical field.

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“…[18][19][20][21] In addition the LCST of PNIPAAm can be tuned easily to a desired temperature by incorporating a suitable comonomer. [22][23][24][25] The peptide selected is the ionic complementary octa-peptide FEFEFKFK, where F is phenylalanine, E is glutamic acid and K is lysine. This peptide is known to form a three-dimensional beta-sheet rich fibrillar hydrogel at 30 g L À1 in water, at room temperature and its gelation is reversible; the gel melting at B75 1C.…”

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confidence: 99%