Synthesis Of Dye Labelled Thermoresponsive Block Copolymers By Raft Polymerization PDF Download
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Author | : Mariana Beija |
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Total Pages | : 0 |
Release | : 2009 |
Genre | : |
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Download Synthesis of -dye-labelled Thermoresponsive Block Copolymers by Raft Polymerization Book in PDF, ePub and Kindle
Double hydrophilic diblock copolymers comprising a thermoresponsive block have gained increasing attention due to their capability of self-assembling in micelles by a temperature change. However, very few fluorescence studies were devoted to investigate their conformation and dynamics both at the air-water interface and in aqueous solutions. In this work, block copolymers composed of a thermoresponsive block of N,N- iethylacrylamide (DEA) and a hydrophilic block of N,N-dimethylacrylamide (DMA) or a reactive block [statistical copolymer of DMA and N-acryloxysuccinimide (NAS)] were prepared by RAFT polymerization. These block copolymers were functionalized at the hydrophilic chain-end by a Rhodamine B or Malachite Green dye using either a pre- or a post-polymerization strategy. In the first case, Rhodamine B and Malachite Green amino derivatives were synthesized for the preparation of dyelabelled chain transfer agent (CTA), which led directly the alpha-dye-labelled block copolymers. Alternatively, the block copolymers were prepared using a precursor CTA and further functionalized with the dye amino derivative. The thermoresponsive behaviour of these polymers and of amphiphilic block copolymers of DEA and N-decylacrylamide was studied at the air-water interface and in Langmuir-Blodgett films using AFM and confocal fluorescence microscopy. Fluorescence emission and anisotropy, light scattering and 1H NMR studies were performed to investigate their behaviour in aqueous solutions.
Author | : Jan Weiss |
Publisher | : |
Total Pages | : 157 |
Release | : 2011 |
Genre | : |
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Download Synthesis and Self-assembly of Multiple Thermoresponsive Amphiphilic Block Copolymers Book in PDF, ePub and Kindle
In the present thesis, the self-assembly of multi thermoresponsive block copolymers in dilute aqueous solution was investigated by a combination of turbidimetry, dynamic light scattering, TEM measurements, NMR as well as fluorescence spectroscopy. The successive conversion of such block copolymers from a hydrophilic into a hydrophobic state includes intermediate amphiphilic states with a variable hydrophilic-to-lipophilic balance. As a result, the self-organization is not following an all-or-none principle but a multistep aggregation in dilute solution was observed. The synthesis of double thermoresponsive diblock copolymers as well as triple thermoresponsive triblock copolymers was realized using twofold-TMS labeled RAFT agents which provide direct information about the average molar mass as well as residual end group functionality from a routine proton NMR spectrum. First a set of double thermosensitive diblock copolymers poly(N-n-propylacrylamide)-b-poly(N-ethylacrylamide) was synthesized which differed only in the relative size of the two blocks. Depending on the relative block lengths, different aggregation pathways were found. Furthermore, the complementary TMS-labeled end groups served as NMR-probes for the self-assembly of these diblock copolymers in dilute solution. Reversible, temperature sensitive peak splitting of the TMS-signals in NMR spectroscopy was indicative for the formation of mixed star-/flower-like micelles in some cases. Moreover, triple thermoresponsive triblock copolymers from poly(N-n-propylacrylamide) (A), poly(methoxydiethylene glycol acrylate) (B) and poly(N-ethylacrylamide) (C) were obtained from sequential RAFT polymerization in all possible block sequences (ABC, BAC, ACB). Their self-organization behavior in dilute aqueous solution was found to be rather complex and dependent on the positioning of the different blocks within the terpolymers. Especially the localization of the low-LCST block (A) had a large influence on the aggregation behavior. Above the first cloud point, aggregates were only observed when the A block was located at one terminus. Once placed in the middle, unimolecular micelles were observed which showed aggregation only above the second phase transition temperature of the B block. Carrier abilities of such triple thermosensitive triblock copolymers tested in fluorescence spectroscopy, using the solvatochromic dye Nile Red, suggested that the hydrophobic probe is less efficiently incorporated by the polymer with the BAC sequence as compared to ABC or ACB polymers above the first phase transition temperature. In addition, due to the problem of increasing loss of end group functionality during the subsequent polymerization steps, a novel concept for the one-step synthesis of multi thermoresponsive block copolymers was developed. This allowed to synthesize double thermoresponsive di- and triblock copolymers in a single polymerization step. The copolymerization of different N-substituted maleimides with a thermosensitive styrene derivative (4-vinylbenzyl methoxytetrakis(oxyethylene) ether) led to alternating copolymers with variable LCST. Consequently, an excess of this styrene-based monomer allowed the synthesis of double thermoresponsive tapered block copolymers in a single polymerization step.
Author | : Binxin Li |
Publisher | : |
Total Pages | : 218 |
Release | : 2008 |
Genre | : |
ISBN | : 9780494588048 |
Download Synthesis and Characterization of Dye-labeled Copolymers by Reversible Addition-fragmentation Transfer (RAFT) Polymerization Book in PDF, ePub and Kindle
Copolymers of N-(2-hydroxypropyl)methacrylamide (HPMA) and N-hydroxysuccinimide methacrylate (NMS) were synthesized by reversible addition-fragmentation transfer (RAFT) polymerization using a semi-batch method. The copolymers were prepared in a wide range of molecular weights (Mn = 4,200-14,000 g/mol) with narrow polydispersities (1.2-1.4). A new approach was developed to prepare a modified RAFT chain transfer agent, a naphthalimide-dye-labeled dithiobenzoate. It was used to prepare a naphthalimide-dye end-labeled poly(HPMA-co-NMS). The copolymer was characterized by four different methods, 1H NMR spectroscopy via end group characterization and using 3-(trimethylsilyl)propionic acid-d 4 sodium salt (TSP) external standard, end group analysis by UV-Vis spectroscopy and by GPC. The results obtained from these measurements are in good agreement.
Author | : Senbin Chen |
Publisher | : |
Total Pages | : 0 |
Release | : 2012 |
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Download Synthesis of Original Block Copolymers by Combination of RAFT Polymerization and Supramolecular Self-assembly Book in PDF, ePub and Kindle
This work dealt with the preparation and the study of supramolecular block copolymers based on hydrogen-bonding between homocomplementary or heterocomplementary stickers. The synthetic strategy was based on the combination of RAFT-mediated controlled radical polymerization and supramolecular chemistry. In the Chapter 2, we developed a strategy relying on the design of RAFT agents bearing thymine/diaminopyridine (DAP) recognition pairs and capable to grow well-defined miktoarm star supramolecular copolymers. To further extend the scope of H-bonding RAFT agents, in the Chapter 3, we also investigated the preparation of RAFT agents functionalized with motifs exhibiting very high binding constants. The Hamilton/barbiturate couple (log(K)≈4-5) was selected to generate more stable supramolecular block copolymers. Aiming at elaborating original associating macromolecules and at simplifying the strategy of synthesis, we finally explored the preparation ABC triblock supramolecular copolymers based on PA11 oligomers (OPA11) in Chapter 4. Ligation of a relevant dithiobenzoate group on the oligomers afforded oligomeric RAFT agents that allow for the preparation of ABC triblock supramolecular copolymers, where A is semi-crystalline, B in rubbery state and C in glassy state. Studies on the incorporation of such copolymers in epoxy networks are under progress.
Author | : Murat Mertoğlu |
Publisher | : |
Total Pages | : 140 |
Release | : 2005 |
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Download The Synthesis of Well Defined Functional Homo- and Block Copolymers in Aqueous Media Via Reversible Addition Fragmentation Chain Transfer (RAFT) Polymerization Book in PDF, ePub and Kindle
Author | : Angela Bowes |
Publisher | : |
Total Pages | : 356 |
Release | : 2007 |
Genre | : Addition polymerization |
ISBN | : |
Download Novel Synthesis of Block Copolymers Via the RAFT Process Book in PDF, ePub and Kindle
Author | : Nor Arbani Sean |
Publisher | : |
Total Pages | : 42 |
Release | : 2015 |
Genre | : |
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Download Synthesis and Characterization of Poly (methacrylamide-styrene) Block Copolymer Via Free Radical Polymerization and Reverse Addition-fragmentation Chain Transfer (raft) Polymerization Book in PDF, ePub and Kindle
Author | : Thomas Martyn Legge |
Publisher | : |
Total Pages | : 436 |
Release | : 2007 |
Genre | : |
ISBN | : |
Download Synthesis and Characterisation of ABA Block Copolymers from Difunctional RAFT Precursors Book in PDF, ePub and Kindle
The design and synthesis of difunctional chain transfer agents and their subsequent use in the manufacture of ABA block copolymers was investigated. The polymerisations of methyl methacrylate, n-butyl methacrylate and n-butyl acrylate and the kinetics of their polymerizations when using a difunctional chain transfer agent were studied. Block extension experiments were performed in order to produce ABA block copolymers. Alternative strategies are explored for the synthesis of ABA block copolymers, by preparation of macro chain transfer agents through the modification of the end groups of commercially available homo- and alternating telechelic polymers bearing hydroxy end groups. The synthesis of functional chain transfer agents bearing azide groups, for potential use in block copolymer synthesis was investigated. The thermal stability of a variety of chain transfer agents was assessed for the purposed of determining their suitability for use at elevated temperatures.
Author | : Matthew Grady Kellum |
Publisher | : |
Total Pages | : 266 |
Release | : 2010 |
Genre | : Copolymers |
ISBN | : |
Download Aqueous RAFT Synthesis of Stimuli-responsive, Amphiphilic Block Copolymers and Self-assembly Behavior in Solution and Incorporation Into LBL Films Book in PDF, ePub and Kindle
Author | : Wei Zhao |
Publisher | : |
Total Pages | : |
Release | : 2014 |
Genre | : Addition polymerization |
ISBN | : |
Download Amphiphilic Block Copolymer Synthesis Via RAFT Polymerization and Their Self-assembly Behavior Book in PDF, ePub and Kindle