Synthesis of reponsive homo- and block copolymers, application to the generation of inorganic-organic nanohybrids [Elektronische Ressource] / Pierre-Eric Millard. Betreuer: Axel H. E. Müller

Pierre Ognion

Informations

• Publié par: universitat_bayreuth
• Publié le: 01 janvier 2011
• Nombre de lectures: 38
• Langue: Deutsch
• Poids de l'ouvrage: 4 Mo

Extrait

SYNTHESIS OF RESPONSIVE HOMO- AND BLOCK
COPOLYMERS, APPLICATION TO THE GENERATION
OF INORGANIC-ORGANIC NANOHYBRIDS


DISSERTATION

zur Erlangung des akademischen Grades eines
Doktors der Naturwissenschaften (Dr. rer. nat.)
in Fach Chemie der Fakultät für Biologie, Chemie und Geowissenschaften
der Universität Bayreuth


vorgelegt von
Pierre-Eric Millard

Geboren in Troyes / Frankreich


Bayreuth, 2010


























Die vorliegende Arbeit wurde in der Zeit von August 2004 bis September 2008 in
Bayreuth am Lehrstuhl Makromolekulare Chemie II unter der Betreuung von Herrn Prof.
Dr. Axel H. E. Müller angefertigt.







Dissertation eingereicht am: 27.07.2010

Zulassung durch die Promotionskommission: 04.08.2010

Wissenschaftliches Kolloquium: 20.10.2010




Amtierender Dekan: Prof. Dr. Stephan Clemens




Prüfungsausschuss: Prof. Dr. K. Seifert (Vorsitz)
Prof. Dr. A. H. E. Müller (Erstgutachter)
Prof. Dr. A. Böker (Zweitgutachter)
Prof. Dr. R. Kempe


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To my family








The most exciting phrase to hear in science, the one that heralds
the most discoveries, is not "Eureka!" but "That's funny..."
(Isaac Asimov)

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Table of Contents
Table of Contents


Summary/Zusammenfassung 7

1. Introduction 11

2. Overview of this Thesis 49

Individual Contributions to Joint Publications 69

3. RAFT Polymerization of N-Isopropylacrylamide and Acrylic Acid 73
under -Irradiation in Aqueous Media

4. Synthesis of Water-Soluble Homo- and Block Copolymers by 93
RAFT Polymerization under -Irradiation in Aqueous Media

5. Fast ATRP of N-Isopropylacrylamide in Water 139

6. Poly(N-Isopropylacrylamide)-b-Poly(Acrylic Acid) Shell Cross- 155
Linked Micelles Formation and Application to the Synthesis of
Metal-Polymer Hybrids

7. New Water-Soluble Smart Polymer-Silica Hybrid Based on 179
Poly(N-Isopropylacrylamide)-b-Poly(Acrylic Acid)

8. List of Publications 199











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Summary/Zussamenfassung
Summary

Responsive homopolymers and multi-responsive block copolymers were prepared via
reversible addition-fragmentation chain transfer (RAFT) and atom transfer radical
polymerization (ATRP). Self-assembly in solution depending on environmental stimuli
was investigated and exploited to create responsive micelles. New cross-linking strategies
were thoroughly performed in aqueous solution to allow a controlled preservation and a
high shape-persistence of the colloid particles, even when exposed to non-selective
environmental conditions.
The synthesis of poly(N-isopropylacrylamide) (PNIPAAm) was investigated by ATRP
for subsequent polymer-protein nanohybrid generation. This temperature-responsive
polymer was polymerized directly in pure water at a low temperature (4 ºC) by using a
functional ATRP initiator which allows post-polymerization conjugation. Without the
addition of Cu(II), the kinetics were extremely fast, typically less than one minute for a
full conversion. By adjusting the ratio of Cu(I)/(Cu(II) and selecting a very active ligand,
all polymerizations proceeded in a controlled fashion to near quantitative conversion
without evidence of termination.
N-isopropylacrylamide and acrylic acid (AA) were also homopolymerized by RAFT
in aqueous media using a novel strategy. Instead of using a diazo-initiator, which
generally decomposed at high temperatures, -irradiation was used to initiate
polymerization at ambient temperature. This type of radiation has many advantages. A
very tiny and constant amount of radicals can be generated, which is perfect for the
RAFT process. Moreover, the rate of initiation only has a low level of dependence on
temperature and can be used in a wide range of temperatures. Finally, compared to UV-
initiation, -irradiation can penetrate the reaction solution deeper and without evidence of
irreversible decomposition of the dithioester end group. Therefore, RAFT
polymerizations of NIPAAm and AA were achieved with a very good level of control,
even at high monomer conversions.
This new process was then extended to many other water-soluble monomers for
generating homopolymers and block copolymers. Among these, acrylamide, N,N-
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Summary/Zussamenfassung

dimethylacrylamide, 2-hydroxyethyl acrylate and poly(ethylene glycol) methacrylate
gave the best results. This technique proved to be very efficient at generating very long
and narrowly distributed polymers (up to a degree of polymerization of 10,000) and at
designing block copolymers.
High molecular weight PNIPAAm-b-PAA copolymers, synthesized by RAFT
polymerization under -radiation, were used to generate multi-responsive cross-linked
micelles. These block copolymers were self-assembled in water at pH 7 by increasing the
temperature over the lower critical solution temperature. The PNIPAAm became
hydrophobic and formed the micellar core and the hydrophilic PAA block generated the
corona which prevented full aggregation of the system. Then, by amidification at elevated
temperatures of the carboxylic moieties via a trifunctional primary amine, the structure
was found to remain even after cooling down the system. The shell-cross-linked micelles
formed were utilized to generate inorganic-organic nanohybrids by the in situ reduction
of gold or silver salts to generate nanoparticles inside the nanocarrier.
Another strategy of cross-linking was also investigated by using amino-functional
silsesquioxane nanoparticles. In water around neutral pH values and room temperature,
these particles interacted with the carboxylic groups of a high molecular weight
PNIPAAm-b-PAA by hydrogen bonding and ionic interactions to generate an insoluble
complex. Due to the presence of the hydrophilic PNIPAAm block, defined spherical
micelles were obtained. The inorganic-organic particles were successfully cross-linked by
subsequent amidification to preserve the structure, even at a high pH. Different
temperature properties of the hybrids were observed depending on the pH value, due to
the residual charge in the micellar core. At a neutral pH, shrinking of the corona was
observed, while at a high pH (pH 13) a fully reversible aggregation of the system
occurred.








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