A Surface Plasmon Resonance Study of Volume Phase Transitions in <i>N</i>-Isopropylacrylamide Gel Films

Harmon, Marianne E.; Jakob, Thomas; Knoll, Wolfgang; Frank, Curtis W.

doi:10.1021/ma010985k

Cited by 73 publications

(98 citation statements)

References 45 publications

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“…This significant change in OT occurs within the temperature range in which the volume phase transition for poly(NIPAM) is observed. [32,33] After this dramatic decrease in OT, further heating of the system results in a slow, minor increase in OT. The system reaches a plateau in OT at 40°C, after which no changes are observed.…”

Section: Optical Properties Of Oxidized Porous Sio 2 /Poly(nipam) Hybmentioning

confidence: 99%

See 1 more Smart Citation

Confinement of Thermoresponsive Hydrogels in Nanostructured Porous Silicon Dioxide Templates

Segal

Perel'man

Cunin

et al. 2007

Adv Funct Materials

116

164

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A thermoresponsive hydrogel, poly(N‐isopropylacrylamide) (poly(NIPAM)), is synthesized in situ within an oxidized porous Si template, and the nanocomposite material is characterized. Infiltration of the hydrogel into the interconnecting nanoscale pores of the porous SiO2 host is confirmed by scanning electron microscopy. The optical reflectivity spectrum of the nanocomposite hybrid displays Fabry–Pérot fringes characteristic of thin film interference, enabling direct, real‐time observation of the volume phase transition of the confined poly(NIPAM) hydrogel. Reversible optical reflectivity changes are observed to correlate with the temperature‐dependent volume phase transition of the hydrogel, providing a new means of studying nanoscale confinement of responsive hydrogels. The confined hydrogel displays a swelling and shrinking response to changes in temperature that is significantly faster than that of the bulk hydrogel. The porosity and pore size of the SiO2 template, which are precisely controlled by the electrochemical synthesis parameters, strongly influence the extent and rate of changes in the reflectivity spectrum of the nanocomposite. The observed optical response is ascribed to changes in both the mechanical and the dielectric properties of the nanocomposite.

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Section: Optical Properties Of Oxidized Porous Sio 2 /Poly(nipam) Hybmentioning

confidence: 99%

“…[12,16,[29][30][31][32][33][34][35] Poly(NIPAM) exhibits an abrupt volume phase transition upon heating above 31-34°C. The polymer undergoes a temperature-induced collapse from an extended coil conformation to a globular structure, resulting in a substantial decrease in volume.…”

Section: Introductionmentioning

confidence: 99%

Confinement of Thermoresponsive Hydrogels in Nanostructured Porous Silicon Dioxide Templates

Segal

Perel'man

Cunin

et al. 2007

Adv Funct Materials

116

164

View full text Add to dashboard Cite

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“…In addition, other external stimuli have also been shown to influence the VPT temperature, such as pH 5 and pressure. 8 Triggering of the VPT may therefore be possible by changing any of these environmental factors. Several different methods have been utilised to produce surface-grafted poly(NIPAAm) gels, including electron beam, 1,4 thermally induced 13,14 and UV 15 -17 grafting, and plasma-induced cross linking.…”

Section: Introductionmentioning

confidence: 99%

Chemical and thermo‐responsive characterisation of surfaces formed by plasma polymerisation of N‐isopropyl acrylamide

Bullett

Talib

Short

et al. 2006

Surface & Interface Analysis

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Plasma polymerisation of N -isopropyl acrylamide (NIPAAm) presents an exciting route for the production of thermally responsive coatings on a wide variety of substrates for applications in tissue culture and microfluidics. One issue associated with the polymerisation of NIPAAm via plasma polymerisation is the limited volatility of the monomer and the subsequent requirement for monomer and reactor heating to create and maintain the vapour. It is already well established that power is critical in the balance between polymer functionality and coating stability in plasma polymers. However, little is known of how reactor and substrate temperatures may be used to influence the physico-chemical characteristics of polymers produced from such low-volatility monomers. In this paper, we examine the effects of a range of plasma deposition parameters on the functionality and stability of plasma-polymerised NIPAAm surfaces. X-ray photoelectron spectroscopy (XPS), near-edge X-ray absorption fine structure spectroscopy (NEXAFS), ellipsometry and contact angle goniometry have been used to examine coating chemistry, stability in aqueous environments, deposition rates and thermo-responsive behaviour. Our results indicate that plasma polymerisation at low powers and low temperatures enhances the ability of plasma-polymerised NIPAAm to display a wettability phase transition, but also contributes to instability of the coating to dissolution or delamination in water. Our spectroscopic measurements confirm that retention of the monomer structure is facilitated by low power and temperature deposition and reveal that conversion of the amide groups to amine and nitrile groups occurs during the polymerisation process, particularly at high discharge powers.

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“…12 The expansion occurs only in one dimension, however, so that the overall volumetric swelling of a thin gel confined to a surface is many times less than in the unconfined case. [12][13][14] Thus, there remains a strong osmotic driving force for swelling of the confined polymer network in the dimensions parallel to the plane of the film, putting the film into a state of biaxial compressive stress. Such swelling stresses can be quite large and have been observed to give rise to mechanical instabilities that lead to wrinkling of the free surface of confined gels 15 and delamination of thin polymer layers from their supporting substrates.…”

Section: Introductionmentioning

confidence: 99%

Template Cross-Linking Effects on Morphologies of Swellable Block Copolymer and Mesostructured Silica Thin Films

2005

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Mesostructured silica films were formed from cross-linked poly(d8-styrene-block-2-vinylpyridine) (dPS-b-P2VP) diblock copolymer template films by swelling with silica precursor solutions. The mesoscopic and macroscopic morphologies of the resulting materials depended strongly on the extent of P2VP cross-linking. Without cross-linking, extensive rearrangement of the initial 2D hexagonal arrangement of dPS cylinders took place during swelling, leading to wormlike mesostructures. At low extents of template cross-linking, osmotic stresses led to a surface-wrinkling instability with a morphology directed by the anisotropic mechanical properties of the swelled block copolymer mesostructure. At higher degrees of P2VP cross-linking, wrinkling was suppressed, and the composite silica/polymer mesostructures corresponded to essentially affine expansions of the initial template structures normal to the film plane. At low extents of P2VP cross-linking, the mesostructures of the hybrid block copolymer/silica films were preserved during oxidation and removal of the block copolymer template species, leading to stable mesoporous silica films. At high extents of P2VP cross-linking, however, insufficient amounts of silica were incorporated to form stable porous inorganic materials, leading to mesostructural collapse. An intermediate level of cross-linking allowed the preparation of stable mesoporous silica films with structures that closely resembled those of the initial template films.

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A Surface Plasmon Resonance Study of Volume Phase Transitions in N-Isopropylacrylamide Gel Films

Cited by 73 publications

References 45 publications

Confinement of Thermoresponsive Hydrogels in Nanostructured Porous Silicon Dioxide Templates

Confinement of Thermoresponsive Hydrogels in Nanostructured Porous Silicon Dioxide Templates

Chemical and thermo‐responsive characterisation of surfaces formed by plasma polymerisation of N‐isopropyl acrylamide

Template Cross-Linking Effects on Morphologies of Swellable Block Copolymer and Mesostructured Silica Thin Films

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