A versatile characterization of poly(N-isopropylacrylamide-co-N,N'-methylene-bis-acrylamide) hydrogels for composition, mechanical strength, and rheology

Chetty, Avashnee; Kovács, János; Sulyok, Zsolt; Mészáros, Á.; Fekete, Jenő; Domján, Attila; Szilágyi, András; Vargha, Viktória

doi:10.3144/expresspolymlett.2013.9

Cited by 21 publications

(20 citation statements)

References 23 publications

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“…After the plasma copolymerization process, the obtained polymeric coatings are immersed in distilled water for 24 h to remove pNIPAAm and poly( N , N ″‐methylene‐bis‐acrylamide) (pMBA) homopolymers and non‐reacted NIPAAm and MBA monomers as they are all water soluble in contrast to p(NIPAAm‐co‐MBA) . During this purification process, water was refreshed every few hours and pure p(NIPAAm‐co‐MBAm) coatings are finally obtained.…”

Section: Methodsmentioning

confidence: 99%

“…The initial results implied that the pNIPAAm coatings possessed an asymmetric structure with a complex mixture of NIPAAm monomers and lineal pNIPAAm homopolymers apart from pNIPAAm crosslinked network situated in the outer layer of the coatings. It is already known that the polymerization of NIPAAm in the presence of crosslinking monomers improves the mechanical properties and response rate of pNIPAAm hydrogels . On the other hand, an excessive crosslinking may compromise the swelling properties and porosity of the hydrogel thus diminishing its potential for biomedical applications .…”

Section: Introductionmentioning

confidence: 99%

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Synthesis of Thermo-Sensitive Hydrogels from Free Radical Copolymerization of NIPAAm with MBA Initiated by Atmospheric Plasma Treatment

Jovančić

Vílchez

Molina

2015

Plasma Process. Polym.

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Thermo-sensitive hydrogels from free radical copolymerization of NIPAAm and crosslinking monomer MBA (p(NIPAAm-co-MBA)) using in situ liquid atmospheric DBD plasma are successfully synthesized as revealed by FTIR and solid state 13 C-NMR analysis, despite a rather short polymerization time of 10 min. The addition of MBA crosslinking monomer exerts a positive influence on the p(NIPAAm-co-MBA) copolymerization process, particularly at higher monomer concentrations and incident plasma power as suggested by GPC analysis. The swelling capacity of the p(NIPAAm-co-MBA) hydrogels declines significantly when the MBA concentration increased due to better crosslinking efficiency during the copolymerization process. The decrease in swelling capacity of p(NIPAAm-co-MBA) is also displayed by cryo-SEM analysis as smaller pore sizes and higher pore density of hydrogels were detected. The thermo responsiveness of p(NIPAAm-co-MBA) hydrogels is confirmed by DSC analysis with LCST values similar to the LCTS value of p(NIPAAm) around 32 8C. Enthalpy /J/g : 58,5924 (Endothermic effect) Exo Peak: 32.8140 o C Onset point: 26.5695 o C Enthalpy: 26.4631 J/g Peak: 33.2749 o C Onset point: 30.6265 o C Enthalpy: 69.6224 J/g Peak: 33.5454 o C Onset point: 21.9078 o C Enthalpy: 58.5924 J/g Peak: 33.0978 o C Onset point: 30.6117 o C Enthalpy: 59.0967 J/g Figure 6. DSC thermograms of the p(NIPAAm-co-MBA) hydrogels obtained at 30 W plasma power with (a) 10% NIPAAm with 0.1% MBA, (b) 10% NIPAAm with 1% MBA, (c) 20% NIPAAm with 0.2% MBA, and (d) 20% NIPAAm with 2% MBA (heating rate of 1.5 8C min À1 from 5 to 50 8C).

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Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Synthesis of Thermo-Sensitive Hydrogels from Free Radical Copolymerization of NIPAAm with MBA Initiated by Atmospheric Plasma Treatment

Jovančić

Vílchez

Molina

2015

Plasma Process. Polym.

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“…Chetty and co-workers investigated the relation between the initial monomer composition and the composition of the formed cross-linked PNIPAAm hydrogel. It has been found that the copolymer gel composition was very close to the initial monomer composition [20]. Therefore the copolymer cross-link density can also be expressed with the monomer to cross-linker ratio, namely with the R values, i.e.…”

Section: Introductionmentioning

confidence: 85%

“…For determining the LCST turbidimetry, calorimetry, light scattering, nuclear magnetic resonance spectroscopy (NMR), oscillation rheometry [20], fluorescence spectroscopy, Fourier transform infrared spectroscopy may be used [21].…”

Section: Introductionmentioning

confidence: 99%

Novel Method to Monitor the De-Swelling of PNIPAAm Hydrogels of Different Cross-Link Density

Karnok¹,

Németh²,

Vargha³

2016

AJAC

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The effect of cross-linker (methylene-bis-acrylamide) (MBA) on the volume phase transition, mechanical properties and de-swelling of Poly(N-isopropyl acrylamide-co-methylene-bis-acrylamide) hydrogel (PNIPAAm/MBA hydrogel) was investigated. A new method, namely isothermal thermogravimetry was developed for monitoring de-swelling of PNIPAAm/MBA hydrogel. Monomer/ Cross-linker ratio of the initial monomer composition R = moleNIPAAm/moleMBA was introduced. It has been proven earlier that initial monomer composition is close to the copolymer composition; hence R values may be used to express cross-link density. Hydrogels from R10 to R150 were investigated. The results of DSC analysis revealed that the less the cross-linker ratio in the gel (from R10 to R150) the more sharp the temperature range of volume phase transition and the higher its enthalpy. Cross-link density, namely increasing cross-linker content in the copolymer (R from 150 to 10) does not significantly affect the temperature range of volume phase transition. It sets on at 33˚C -34˚C, and ends between 35˚C and 38˚C. Cross-link density has significant effect on compression modulus. By decreasing the ratio of cross-linker (by increasing R from 10 to 150), the compression modulus increases, goes through a maximum, and then decreases. The highest compression modulus was measured for PNIPAAm/MBA hydrogel R20. Hydrogels with cross-linker content between R100 and 30 are strong enough and have their thermoresponsivity. Isothermal thermograms of de-swelling are of similar character for all the gels with different cross-linker content. During the initial stage of de-swelling for gels with higher cross-linker content (R10 -R15) the solute release is quicker than for gels R20 -150 and the thermograms are drawn out. In the initial stage of de-swelling, i.e. during the first 40 minutes the rate of solute release is the highest for gels R70 -150. The cross-linker content effects solute release, especially for gels with high crosslinker content. It is noteworthy that gels R10 -15 release solute quicker than gels R30 -50 and * Corresponding author. N. Karnok et al. 307their rate of de-swelling is comparable to that of gels R100 -150. The novel thermogravimetric method enables the selection of gels based on the rate of solute release and it can also be applied for other cross-linked gels.

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“…Chetty and co-workers observed that the critical strain increases from 1.6% to 7.9% with increasing cross-linker ([BIS]/[NIPAAM]) concentration from 0.01 to 0.1. 41 However, in the present system the critical strain increases from 203% to 584% with the addition of 3 mM R solution. This signicant increase of critical strain is an interesting observation particularly for the case of supramolecular crosslinking.…”

Section: Mechanical Propertiesmentioning

confidence: 96%

Rheological and fluorescent properties of riboflavin–poly(N-isopropylacrylamide) hybrid hydrogel with a potentiality of forming Ag nanoparticle

et al. 2014

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The riboflavin (R) and poly(N-isopropylacrylamide) (PNIPAAM) hybrid hydrogels have been prepared using the free radical polymerization of N-isopropylacrylamide in the presence of N,N 0 -methylene bisacrylamide as a cross linker for 1, 2 and 3 mM concentrations of R. The invariance of storage (G 0 ) and loss (G 00 ) moduli over a wide range of angular frequency, where G 0 > G 00 for R-PNIPAAM system characterize it to be behaving as a gel in the hybrid state. Both G 0 and G 00 decrease with the increase of R concentration, but the decrease is four times higher in the former than in the latter. R-PNIPAAM gel has a higher critical strain value than PNIPAAM gels and it gradually increases with the increase in R concentration indicating that R is acting as a supramolecular cross-linker. The fluorescent intensity of R-PNIPAAM gels increases with the increase in R concentration and its variation with temperature at different pH shows an increase in the intensity value with temperature, showing the maximum at $30 C because of the coil-to-globule transition of PNIPAAM chains, suggesting that the R-PNIPAAM gel can be used to be a probe for temperature detection. The sensitivity index of the fluorescent temperature sensing of R-PNIPAAM gel is moderate and it is highest at pH 7. R becomes gradually released from the R-PNIPAAM gel when dipped into water (pH 7) at 20 C, initially at a slower rate, then at a higher rate, and finally it shows a leveling for the release of 19% of embedded R at 24 h of aging. Silver nanoparticles that are grown in the R-PNIPAAM gels by immersing the slashed gel pieces in AgNO 3 solution stay at both the surface and the interior of the R-PNIPAAM fibres, maintaining the gel structure intact with a decrease in critical strain and causing a quenching of the fluorescence intensity of R-PNIPAAM gels. The average size and size distribution of AgNPs linearly increase with R concentration at a constant AgNO 3 concentration.

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A versatile characterization of poly(N-isopropylacrylamide-co-N,N'-methylene-bis-acrylamide) hydrogels for composition, mechanical strength, and rheology

Cited by 21 publications

References 23 publications

Synthesis of Thermo-Sensitive Hydrogels from Free Radical Copolymerization of NIPAAm with MBA Initiated by Atmospheric Plasma Treatment

Synthesis of Thermo-Sensitive Hydrogels from Free Radical Copolymerization of NIPAAm with MBA Initiated by Atmospheric Plasma Treatment

Novel Method to Monitor the De-Swelling of PNIPAAm Hydrogels of Different Cross-Link Density

Rheological and fluorescent properties of riboflavin–poly(N-isopropylacrylamide) hybrid hydrogel with a potentiality of forming Ag nanoparticle

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