Photoreactive polyorganosiloxane nanoparticles and the fabrication of photocleavable microcapsules [Elektronische Ressource] / Xiaofeng Yuan

Informations

• Publié par: johannes_gutenberg-universitat_mainz
• Publié le: 01 janvier 2005
• Nombre de lectures: 8
• Langue: English
• Poids de l'ouvrage: 11 Mo

Extrait

Photoreactive Polyorganosiloxane
Nanoparticles and the Fabrication of
Photocleavable Microcapsules



Dissertation

Zur Erlangung des Grades
“Doktor der Naturwissenschaften”








Am Fachbereich Chemie, Pharmazie und Geowissenschaften
der Johannes Gutenberg-Universität Mainz




Xiaofeng Yuan

geb. in Hunan, P. R. China







Mainz 2005






Die vorliegend Arbeit wurde in der Zeit vom:
August 2002 bis zum Juli 2005
am Institut für Physikalische Chemie
der Johannes Gutenberg-Universität Mainz
angefertigt.



















Dekan: Prof. Dr. Peter Langguth



Tag der mündlichen Prüfung: 14 July 2005 CONTENTS

1 INTRODUCTION ................................................................................................1
1.1 Colloids ...........................................................................................................1
1.1.1 Characteristics of colloidal dispersions …...............................................1
1.1.2 Colloid stability .......................................................................................3
1.1.3 Aggregation and clustering of colloids ...................................................5
1.1.4 Colloid assemblies ..................................................................................6
1.2 microcapsules and controlled release ...............................................................8
1.4 Goal of this work .............................................................................................8

2 METHODS ..............................................................................................................10
2.1 Light Scattering .............................................................................................10
2.1.1 Static light scattering ........................................................................ 10
2.1.2 Dynamic light scattering ...................................................................15
2.2 UV curing ......................................................................................................16
2.3 Microscopy.....................................................................................................18
2.3.1 Optical Microscopy ...............................................................................18
2.3.2 Fluorescence Confocal Microscopy ......................................................19
3.3.3 Electron Microscopy .............................................................................20
2.3.4 Atomic Force Microscope (AFM)..........................................................22
2.4 UV-VIS Spectroscopy ...................................................................................25
2.5 Fluorescence Spectroscopy ...........................................................................26
2.6 GPC and FFF .................................................................................................29
2.6.1 Gel Permeations Chromatography (GPC) ..............................................29
2.6.2 Asymmetrical Flow Filed-Flow-Fractionation (A-Fl-FFF) ...................30

3 DYE-LABELLED POLY(ORGANOSILOXANE) NANOPARTICLES .............32
3.1 Polyorganosiloxane µ-gels .............................................................................32
3.1.1 Hydrolysis and Condensation of Alkoxysilane.......................................33
3.1.2 Polycondensation of alkoxysilanes in µ-emulsion .................................34
3.1.3 Redispersible Polyorganosiloxane- µ-Gels ............................................ 37
i3.2 Dye-labelled Polyorganosiloxane- µ-gels .......................................................39
3.2.1 Coumarin 343 Labelled polyorganosiloxane-µ-gel ..............................45
3.2.2 Coumarin labeled polyorganosiloxane- µ-gels ......................................48
3.2.3 Cinnamate Labelled polyorganosiloxane ..............................................50

4 REVERSIBLE CLUSTER FORMATION INDUCED BY INTERMOLECULAR
PHOTODIMERIZATION OF NANOPARTICLES ................................................53
4.1 Reversible Photodimerization ........................................................................55
4.1.1 Photodimerization of Coumarin derivatives ...........................................58
4.1.2 Photodimerization of Cinnamate Derivatives ........................................59
4.2 Cluster formation induced by inter-particle photo-dimerization ....................60
4.3 Reversible Cluster Formation .........................................................................67
4.3.1 Reversible Cluster Formation of cinnamate labelled particle ................67
4.3.2 Reversible Cluster Formation of coumarine labelled particles ..............73
4.4 Effect of optical filters on Cluster Formation References ..............................74
4.5 Effect of dye content on Cluster Formation ...................................................77
4.6 Solvent Effect on the Cluster Formation ........................................................78
4.7 Optimization of Irradiation Conditions ..........................................................81
4.7.1 Investigation of irradiated dye-labeled nanoparticles by UV-vis
Spectroscop .....................................................................................................81
4.7.2 Toluene bath as a novel optical filter .....................................................83
4.7.3 Combination of toluene bath and dichroic mirror ..................................84

5 PHOTOCLEAVABLE ORGANOSILICON MICROCAPSULES BUILT FROM
PHOTOREACTIVE NANOPARTICLES ….....................................................89
5.1 Water/Oil/Water emulsion .............................................................................91
5.1.1 Introduction ............................................................................................91
5.1.2 Preparation of Water/Oil/Water emulsions ............................................93
5.2 Photoclevable Microcapsules built from photoreactive polyorganosiloxane- µ-
gels, based on a w/o/w emulsion template ........................................................102
5.2.1 Formation of Microcapsules .................................................................102
5.2.2 Photocleavage of Microcapsules ..........................................................108
ii5.2.3 Controllable Shell Thickness of Microcapule ......................................112

6. ENCAPSULATION AND RELEASE TEST ....................................................115
6.1 Release reagent study ...........................................…....................................117
6.2 Photophysics of cyclodextrin inclusion complexes ......................................119
6.3 Results and discussion ..................................................................................122

7. SUMMARY AND OUTLOOK ..........................................................................126
7.1 Summary ......................................................................................................126
7.2 Outlook .........................................................................................................127

8. EXPERIMENTAL ....................................................................................... 130
8.1 Materials .......................................................................................................130
8.2 Synthesis ....................................................................................................131
8.2.1 Chlorobenzyl-Functionalized Poly(organosiloxane) Nanoparticles.....131
8.2.2 Labeling reaction ..................................................................................132
8.2.2.1 Cesium salt of p-nitro cinnamate .............................................133
8.2.2.2 Cesium salt of (7-coumaryloxy)acetate ...................................134
8.2.3 Photodimerization ...............................................................................137
8.2.4 Photocleavage Reaction .......................................................................138
8.2.5 Preparation of the water/oil/water-emulsion ........................................139
8.2.6 Fixing the microcapsules by photodimerization of the photoreactive
nanoparticles ..................................................................................................139
8.2.7 Destroying the microcapsules by photocleavage .................................140
8.2.8 Preparation of cyclodextrin-filled microcapsules and quantification of
release after photocleavage ...........................................................................140
8.3 Characterization ............................................................................................140
8.3.1 Dynamic and Static Light Scattering ....................................................141
8.3.2 Gel Permeation Chromatography