Thermal micro ATR/FT-IR spectroscopic system for quantitative study of the molecular structure of poly(N-isopropylacrylamide) in water

Lin, Shan‐Yang; Chen, Ko-Shao; Liang, Run-Chu

doi:10.1016/s0032-3861(98)00512-6

Cited by 212 publications

(166 citation statements)

References 33 publications

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“…This effect can be explained by the competition between intermolecular REVIEW and intramolecular hydrogen bonding below and above the LCST. [110] At temperatures below the LCST the predominantly intermolecular hydrogen bonding contributes to the hydrophilicity of PNIPAAm films whereas at temperatures above the LCST increased intramolecular hydrogen bonding results in hydrophobic films. The switch between inter-and intramolecular hydrogen bonding involves the bistable states with multi-weak-interactions.…”

Section: Single-responsive Interfacesmentioning

confidence: 99%

Bio‐Inspired, Smart, Multiscale Interfacial Materials

2008

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In this review a strategy for the design of bioinspired, smart, multiscale interfacial (BSMI) materials is presented and put into context with recent progress in the field of BSMI materials spanning natural to artificial to reversibly stimuli‐sensitive interfaces. BSMI materials that respond to single/dual/multiple external stimuli, e.g., light, pH, electrical fields, and so on, can switch reversibly between two entirely opposite properties. This article utilizes hydrophobicity and hydrophilicity as an example to demonstrate the feasibility of the design strategy, which may also be extended to other properties, for example, conductor/insulator, p‐type/n‐type semiconductor, or ferromagnetism/anti‐ferromagnetism, for the design of other BSMI materials in the future.

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Section: Single-responsive Interfacesmentioning

confidence: 99%

Bio‐Inspired, Smart, Multiscale Interfacial Materials

2008

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“…This unique system has been used in our laboratory to investigate the correlation between the structural change of samples (such as drug, 15) skin, 16) silicon elastomer, 17) Eudragits and poly(N-isopropylacrylamide) polymers, [18][19][20] a-crystallin and dipeptide sweetener 21,22) and thermal treatment. Our previous study showed that the pathway of the solid-state diketopiperazine (DKP) formation in aspartame and lisinopril via intramolecular cyclization by the nonisothermal FT-IR microspectroscopic system is almost simultaneous.…”

Section: -14)mentioning

confidence: 99%

Reaction Kinetics of Solid-state Cyclization of Enalapril Maleate Investigated by Isothermal FT-IR Microscopic System.

Wang

Lin

Chen

2001

CHEMICAL & PHARMACEUTICAL BULLETIN

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The stability of drugs in various solid dosage forms is an important issue, since solid dosage forms are the most common pharmaceutical formulation in clinical use. To determine the shelf life of a drug, accelerated stability testing has been performed under exaggerated conditions to examine the degradation process, to make shelf-life predictions and to calculate preliminary expiration dates. [1][2][3] The accelerated stability testing method is largely based on an empirical relationship of temperature to an observed chemical reaction-rate constant. Information about the room-temperature stability is then extrapolated from this accelerated data using the Arrhenius' law. [1][2][3] This test is generally performed under isothermal conditions, using parallel storage of samples at different temperatures.The decomposition reactions of solids include all the chemical transformations, which involve a redistribution of the bonding forces of a crystalline reactant. The bond redistribution process usually occurs at a reaction interface to transform the reactant solid into a product.4) The decomposition reaction-rate of a solid phase is usually assumed to be directly proportional to the area of the active interface and principally relates to the temperature dependency. Once a molecule decomposes at an activated site and changes in geometry, the neighboring molecules are more likely to degrade and cause a further decomposition reaction. In general, the decomposition reactions of solids are too complicated to show the molecular details of the solid-state reaction.5) Some solid-state decompositions of drugs have been analyzed in terms of zero-order and first-order kinetics, 6,7) and both the Prout-Tompkins and Avrami-Erofeev equations have also been found to be the best fit for the decomposition of aspartame, cytosine monohydrate or binaphthyl. 5,8,9) Although many methods of analysis have been used to study solid-state reactions and their kinetics, 10) the combined physical analytical technique of Fourier transform infrared (FT-IR) spectroscopy equipped with a thermal analyzer is more convenient than other methods. 11-14)The thermal-dependent characteristics of materials have been extensively studied using a thermal FT-IR microspectroscopic system, which is a simple, rapid and powerful tool for studying micro-samples.14) It not only determines the effect of temperature on the conformation of samples, but also acts as a method for accelerated stability testing to predict product stability and shelf life. This unique system has been used in our laboratory to investigate the correlation between the structural change of samples (such as drug, 15) skin, 16) silicon elastomer, 17) Eudragits and poly(N-isopropylacrylamide) polymers, [18][19][20] a-crystallin and dipeptide sweetener 21,22) and thermal treatment. Our previous study showed that the pathway of the solid-state diketopiperazine (DKP) formation in aspartame and lisinopril via intramolecular cyclization by the nonisothermal FT-IR microspectroscopic system is almost simulta...

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“…[17] Besides, a new strong absorbance peak appeared at about 1450 cm À1 and can be ascribed to CN stretching. [18] Also, no peak at about 1730 cm À1 assignable to the CO stretching vibration of the ester units occurred, that is, amino groups of CHI as effective binding sites can be grafted to carboxyl groups of RB in a dehydration reaction,…”

mentioning

confidence: 99%

Rose Bengal‐Grafted Biodegradable Microcapsules: Singlet‐Oxygen Generation and Cancer‐Cell Incapacitation

Wang

Zheng

et al. 2011

Chemistry A European J

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Rose bengal-grafted chitosan (RB-CHI), synthesized through dehydration between amino and carboxyl functional groups under mild conditions, was coated onto the outer layer of preformed biodegradable microcapsules consisting of sodium alginate and chitosan. The fabricated photosensitive microcapsules were characterized by optical microscopy, scanning electron microscopy, and confocal laser scanning microscopy. The assembled materials maintained intact spherical morphology and thus showed good ability to form thin films. Electron spin resonance spectroscopy allowed direct observation of the generation of singlet oxygen ((1)O(2)) from photosensitive microcapsules under light excitation at about 545 nm. Furthermore, with increasing light radiation, the content of (1)O(2) increased, as detected by a chemical probe. In vitro cellular toxicity assays showed that RB-CHI-coated photosensitive microcapsules exhibit good biocompatibility in darkness and high cytotoxicity after irradiation, and could provide new photoresponsive drug-delivery vehicles.

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Thermal micro ATR/FT-IR spectroscopic system for quantitative study of the molecular structure of poly(N-isopropylacrylamide) in water

Cited by 212 publications

References 33 publications

Bio‐Inspired, Smart, Multiscale Interfacial Materials

Bio‐Inspired, Smart, Multiscale Interfacial Materials

Reaction Kinetics of Solid-state Cyclization of Enalapril Maleate Investigated by Isothermal FT-IR Microscopic System.

Rose Bengal‐Grafted Biodegradable Microcapsules: Singlet‐Oxygen Generation and Cancer‐Cell Incapacitation

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