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Synthesis and Properties of Photoluminescent Smart Thermo-respinsive Polymernc Hydrogel Nanopartilcles

Author: JiangYingNan
Tutor: LinQuan；YangBai
School: Jilin University
Course: Polymer Chemistry and Physics
Keywords: smart hydrogel polymeric nanoparticles PL thermo-response linear and reversible
CLC: O631.3
Type: PhD thesis
Year: 2011
Downloads: 225
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Abstract


Polymeric materials with responses to external stimuli are of great interest in a number of applications include drug delivery、biolable、bioprobe、thermo-sensor、color-tunable crystals and catalysis. PNIPAM, with a coil-to-globule transition in water at LCST of 32℃, is one of the candidates and has been widely studied most. The coil-to-globule transition of PNIPAM-based responsive system could be a total reversible process.Sensitive and fast monitoring of temperature change is of great importance to the development of bioprobes、chemical valves、drug delivery systems、chemsensors and switches. Usually, various PL organic molecules, nanocrystals and quantum dots were used to engineer the fluorescent PNIPAM hydrogels. The thermo-responsive fluorescence of the reported PNIPAM-based hydrogels was only active in a very narrow temperature window, which was around the LCST. The sudden change of the emission around the LCST, which was documented as an on-off feature, enables the application limitation of these fluorescent PNIPAM hydrogels. There are outstanding needs for fluorescent PNIPAM hydrogels to response effectively and continuously in a broad temperature window without such an on-off element. Therefore, we prepared hybrid thermo-responsive hydroel nanoparticles with their PL intensity reversible, linear, and sensitive to a broad temperature range. We investigated and characterized the PL thermo-response of the hydrogel nanoparticles and discussed their applications in environmental protection, bioprobe and building of functional patterns. In Chapter 2, we designed the hard core to be PS-co-PNIPAM and the soft shell PNIPAM, PS-co-PNIPAM/PNIPAM hydrogel core/shell nanoparticles which were prepared by two steps of emulsion-free copolymerization. Water-soluble Europium organic complex was designed to coordinate in the shell of core/shell hydrogel nanoparticles.. Our bright Eu-doped PS-co-PNIPAM/PNIPAM hydrogel nanoparticles were detected to be linear, reversible and sensitive, regarding the emission intensity but with little change in the emission peak position. Their temperature-stimuli PL response in a broad temperature range is considerably different from that of the previously reported PNIPAM hydrogels and should bring insights into a universal approach to function nal hydrogels with reversible and linear responses to external stimuli, such as micro-thermometers、bioprobes、drug delivery、thermosensors and building of functional patterns with light emission.In Chapter 3, we fabricated the hard core to be PS-co-PNIPAM and the soft shell PNIPAM-AA, PS-co-PNIPAM/PNIPAM hydrogel core/shell nanoparticles.The AA provided the shell of nanoparticles carboxyl group to automatically connected with the AIE-type lumophore, TPE derivative, quaternary ammonium salt 1 by coulomb force. Then the PNIPAM-AA chains could hold the 1 tightly to hamper the freely rotation of the phenyl peripheries. As a result, the amphiphilic 1 at the nanoparticles immediately showed a drastic increase in the PL intensity, more hundreds fold intense than those from 1 solution. Meanwhile, it is remarkable that the PL response of the 1-doped PS-co-PNIPAM/PNIPAM-AA hydrogel nanoparticles is reversible and sensitive to temperature-stimuli which are considerably different from that of the previously reported fluorescent AIE molecules、crystals or films.Furthermore, the nanoparticles with special structures endowed the AIE molecule 1 with bright and controllable PL uniformly dispersed in either polar solution or nonpolar solution. The hydrogel nanoparticles served as a suitable carrier may greatly expand practicality and applicability of the AIE molecules at nanoscale. These novel PL nanoparticles doped with 1 with linear reversible and temperature-sensitivity in a broad temperature range (2℃-80℃) is of great importance to the development of micro-thermometer、explosive detection、biological probing、biological imaging、FL sensors and drug delivery.In Chapter 4, we systematically investigated the PL responses of 1-doped PS-co-PNIPAM/PNIPAM-AA hydrogel nanoparticles to CrO42- selectively at different temperature.The detection of CrO2- is important as the ion can be carried into humban beings cells and cause oxidative damage to DNA. The ion may also be introduced into drinking water through environmental pollution. The analysis showed that the PL intensity of hydrogel core/shell nanoparticles is sensitively weakened by the addition of a small amount of CrO42- in aqueous media. The PL intensity is decreased progressively with an increase in the amount of added CrO42- with highly selective, reached the discharge standard of national wastewater discharge requirements GB8978-1996 of the highest total chromium (1.5 mg/1 level). The PL intensity of the mixed solution decreased with the increase of temperature. The PL thermo-responsive plots showed that the sensitivity of PL intensity to CrO42- at low temperature was higer than at high temperature. It will be very useful in fast sensitively environmental detection, industrial wastewater discharge and water protection.Meanwhile, we investigated the behavior of 1-doped PS-co-PNIPAM/PNIPAM-AA hydrogel nanoparticles as a bioprobe and to find bioprobing systems with higher sensitivities. In BSA、DNA and RNA solutions of the same concentration, all the PL intensity of the solutions decreased. But the PL intensity of RNA mixed solution decreased more than the other two sample above, revealing that the hybrid hydrogel nanoparticles showed higher sensitivity to RNA. Although the PL intensity of the mixed biomolecular solution decreased with the increase of temperature, the PL thermo-response could only be achieved at lower temperature (<LCST) as the mixed emulsion was not stable.On the other hand, we introduce a new approach to prepare a large-area array of specifically periodical regions through assemble of Eu-doped PS-co-PNIPAM/PNIPAM hydrogel nanoparticles, only by controlling environment temperature. Surface property of the particles shells undergoes a hydrophilic to hydrophobic transition below and above LCST. Several drops of latex containing particles spread on a HDT and MHA modified substrate which had a periodical alternative hydrophilic and hydrophobic strips pattern. Large-area two-dimensional assemble with red light emission were obtained simply after drying of water.

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CLC: > Mathematical sciences and chemical > Chemistry > Polymer chemistry ( polymer ) > Polymer physics and physical chemistry of polymers > The chemical nature of polymers
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