Increasing the Dissolution Rate of Polystyrene Waste in Solvent-Based Recycling

Solvent-based recycling of plastic waste is a promising approach for cleaning polymer chains without breaking them. However, the time required to actually dissolve the polymer in a lab environment can take hours. Different factors play a role in polymer dissolution, including temperature, turbulence, and solvent properties. This work provides insights into bottlenecks and opportunities to increase the dissolution rate of polystyrene in solvents. The paper starts with a broad solvent screening in which the dissolution times are compared. Based on the experimental results, a multiple regression model is constructed, which shows that within several solvent properties, the viscosity of the solvent is the major contributor to the dissolution time, followed by the hydrogen, polar, and dispersion bonding (solubility) parameters. These results also indicate that cyclohexene, 2-pentanone, ethylbenzene, and methyl ethyl ketone are solvents that allow fast dissolution. Next, the dissolution kinetics of polystyrene in cyclohexene in a lab-scale reactor and a baffled reactor are investigated. The effects of temperature, particle size, impeller speed, and impeller type were studied. The results show that increased turbulence in a baffled reactor can decrease the dissolution time from 40 to 7 min compared to a lab-scale reactor, indicating the importance of a proper reactor design. The application of a first-order kinetic model confirms that dissolution in a baffled reactor is at least 5-fold faster than that in a lab-scale reactor. Finally, the dissolution kinetics of a real waste sample reveal that, in optimized conditions, full dissolution occurs after 5 min

Synthesis of conjugated block-copolymers: Advanced structures and polymerization methods

pi-Conjugated polymers are a promising class of materials because of the ir exceptional optic and electronic properties. They are used in high te ch applications, e.g. organic solar cells, organic LEDs, supercapa citors, biosensors. Their molecular architecture and structure play a do minant role in their performance and therefore obtaining control over th eir synthesis is one of the main goals polymer chemists pursue nowadays. Building predetermined molecular structures with low molar mass distrib utions was the challenge in the past and will continue to be so in the f uture. The major breakthrough was the discovery of the Kumada catalyst-t ransfer polymerization of P3AT with Ni(dppp)Cl2 as a catalyst by the res earch groups of Yokozawa and McCullough in 2004. A controlled chain-grow th polymerization mechanism was demonstrated for this class of materials nd enabled the possibility to develop block-copolymers and other topologies in a one-pot synthesis. In a first part, this manuscript desc ribes the research performed to quantify the emarkable behavior of the catalyst leading to the chaingrowth character. An in-depth 1H NMR study was used to assign the different end-groups of the polymer ch ains. Next, this polymerization technique is exploited to develop block- copoly(3-alkylthiophene)s in which both blocks exhibit a different solub ility in the solvents used. While the solubility difference in the first set of synthesized block-copoly(3-alkylthiophene)s originates from a di fferent length of the alkyl side chains, a more pronounced and tunable d ifference, based on the presence of amine-functions in one of both block s, is obtained in the next group. The introduction of chiral centers in one of both blocks makes a chiroptical investigation possible. In a next part, the possibility to transform the polymerization of the h elically poly(3,6-[9,10-di(octyloxy)]phenantrene), traditionally synthes ized via a step-growth process, into a controlled polymerization is inve stigated. Therefore, the current chain-growth polymerization techniques presented in literature are applied and investigated using MALDI-ToF spe ctrometry and GPC. Although the current chain-growth mechanisms are well-established for pa rticular classes of conjugated polymers, they are far from universal whi ch hinders the unlimited formation of block-copolymers in a simple one-p ot synthesis. To overcome this issue, a new chain-growth polymerization protocol for the synthesis of conjugated polymers is introduced in the l ast part of this thesis. This protocol, based on a Negishi coupling with a Pd(Ruphos) catalyst, does not rely on any systemdependent interaction s, as was the case for the current mechanisms. After the study on the ch ain-growth behavior of P3AT, poly(3-alkylselenophene) and poly(9,9-dialk ylfluorene), ABC tri-blockcopolymers are synthesized with the new Pd(Rup hos) protocol and assessed with spectroscopic techniques and GPC.1. Introduction 1 2. An introductory tale … 7 3. Conjugated Polymers 11 3.1. Introduction 11 3.2. Optical and electronic properties 12 3.3. Solubility 17 4. Polymerization mechanisms for conjugated polymers 19 4.1. Introduction 19 4.2. Step-growth polymerizations 20 4.3. Chain-growth polymerizations 23 4.4. Conjugated block-copolymers 45 5. Aggregation behavior of conjugated polymers 53 5.1. Macromolecular vs. supramolecular behavior 53 5.2. UV-vis absorption and emission spectroscopy 54 5.3. Chirality in conjugated polymers 55 5.4. Circular dichroism spectroscopy 57 5.5. Chiral random- and block-copolymers 61 6. Aim of the dissertation 69 7. Quantitative analysis of the catalyst ring-walking process. 75 7.1. Introduction 75 7.2. The Kiriy model 76 7.3. Approach 76 7.4. Synthesis of a terthiophene model compound. 80 7.5. Determination of the stickiness parameter 80 7.6. AB- vs. BAB block-copolymers 83 7.7. Conclusion 85 7.8. Experimental Part 86 8. Block-copoly(3-alkylthiophene)s with different side chain lengths 91 8.1. Introduction 91 8.2. Approach 92 8.3. Monomer and polymer synthesis 94 8.4. 1H NMR analysis 96 8.5. Chiroptical analysis 100 8.6. Conclusion 106 8.7. Experimental Part 106 9. Amphiphilic block copoly(thiophene)s 113 9.1. Introduction 113 9.2. Approach 114 9.3. Monomer and polymer synthesis 116 9.4. GPC and 1H NMR analysis 119 9.5. Chiroptical analysis in solution 121 9.6. Chiroptical analysis in film 132 9.7. DSC analysis 140 9.8. Conclusion 141 9.9. Experimental Part 142 9.10. Appendix 149 10. Chain-growth polymerization of poly(phenanthrene)s 157 10.1. Introduction 157 10.2. Approach 158 10.3. Kumada-based mechanisms 159 10.4. Suzuki-based mechanism 160 10.5. Conclusion 170 10.6. Experimental part 171 11. Development of the chain-growth mechanism 177 11.1. Introduction 177 11.2. Approach 179 11.3. Design 180 11.4. Reaction conditions 181 11.5. Monomer synthesis 182 11.6. Synthesis of the initiators 184 11.7. Evaluation of the chain-growth behavior 185 11.8. Decomplexation of the catalyst 192 11.9. Di-block-copolymers 195 11.10. General relevance 198 11.11. Conclusion 199 11.12. Experimental part 200 12. Synthesis of all-conjugated tri-block-copolymers 209 12.1. Introduction 209 12.2. Approach 210 12.3. Choice of the Grignard reagent 210 12.4. Chain-growth character of poly(3-octylselenophene) 219 12.5. Synthesis of tri-block-copolymers 220 12.6. GPC analysis 223 12.7. 1H NMR analysis 226 12.8. UV-vis absorption and fluorescence spectroscopy 228 12.9. Conclusion 231 12.10. Experimental part 232 13. General Conclusion and Perspectives 247 14. Experimental Techniques 255 15. Heath, Safety & Environment 259 16. List of Publications 263nrpages: 312status: publishe

Synthese en eigenschappen van selectief oxideerbare geconjugeerde polymeren

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Chirality in conjugated polymers: when two components meet

Chirality is a well-studied feature in the auspicious class of conjugated polymers. Proper use allows us to study and to control the behavior of the polymers which make them very valuable in many applications. Mostly chiral homopolymers are considered, but what happens when the chirality originates from the interplay between multiple components? This review summarizes different approaches to implement multicomponent chirality in conjugated polymers and their properties. © The Royal Society of Chemistry 2012.status: publishe

Amphiphilic chiral block-copoly(thiophene)s: tuning the blocks

This report describes the synthesis and characterization of amphiphilic block-copoly(3-alkylthiophene)s with one hydrophobic and one hydrophilic block. Implementation of a chiral center in one of the two blocks enables a chiroptical evaluation of the materials in different media. Depending on the solvent conditions, phase-separation and selective aggregation of one of both blocks becomes feasible, which has implications on the aggregation behavior of the second block. The presented chiroptical and thermal study provides an insight into the self-assembly of these materials both in solution and in film. © 2013 The Royal Society of Chemistry.status: publishe

AB Block Copoly(3-alkylthiophenes): Synthesis and Chiroptical Behavior

In a first part of this article, the synthesis of AB type block copoly(3-alkylthiophene)s initiated by Ni(dppp)Cl-2, the most commonly used initiator for these polymers, is investigated. For this study the respective H-1 NMR resonances of all possible end-groups are identified. This result confirms the hypothesis that the Ni(dppp) species can walk back to the beginning of the polymer chain and that propagation can occur at both chain ends. The next part of the article studies the chiroptical behavior of AB-type block copoly(3-alkylthiophene)s with one chiral block and compares the results with those of the corresponding random copolymers. In order to obtain exclusively AB-type block copolymers, the polymers were prepared from a modified Ni initiator. They all have the same degree of polymerization but vary in the length of the respective blocks. The chiroptical behavior was studied by changing the ratio solvent/nonsolvent, meanwhile monitoring the UV-vis and circular dichroism (CD) spectra. Three series were investigated: one in which both blocks aggregate simultaneously, one in which the achiral block stacks before the chiral block, and one in which the chiral block stacks first followed by the achiral block. It was found that when the blocks stack independently, the (chiral/achiral) stacking of the latter is significantly influenced by the former. If both blocks of the polymer chains aggregate simultaneously, Cotton effects which are significantly larger than those of the chiral homopolymer are found.status: publishe

Synthesis, Chiroptical Behavior, and Sensing of Carboxylic Acid Functionalized.Poly(phenylene ethynylene-alt-bithiophene)s

Several poly(phenylene ethynylene-alt-bithiophene)s with (chiral) nonfunctionalized substituents were synthesized with a variable phenylene ethynylene (PE) spacer length (up to 4 repeating units). The chiroptical behavior was evaluated with UV vis and circular dichroism (CD) spectroscopy, revealing a highly solvent-sensitive aggregate formation. Based on this high sensitivity, both chiral and achiral carboxylic acid functionalized analogues were prepared, of which the length of the spacer connecting the carboxylic acid to the polymer backbone was varied. A combination of UV vis, CD, and emission spectroscopy showed a clear affinity of chiral amines toward the functionalized polymers both in solution and in film. However, a different supramolecular behavior of the polymers was observed depending on the length of the carboxylic acid functionalized side chain.status: publishe

Quest for a universal controlled chain-growth polymerization protocol: Toward a variety of all-conjugated block-copolymers

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Development of a Universal Chain-Growth Polymerization Protocol of Conjugated Polymers: Toward a Variety of All-Conjugated Block-Copolymers

This manuscript reports a universal chain-growth polymerization protocol for conjugated polymers. Herein, the Pd-based catalyst moiety dissociates from the growing active center into the solution and therefore, the controlled chain-growth character is not relying on any specific, system-related complexation, as is the case in polymerization methods reported before. This makes the protocol applicable on a broad range of monomers and, furthermore, also allows an easy one-pot synthesis of block-copolymers by successive monomer addition. A chain-growth polymerization mechanism for poly(3-hexylthiophene) (P3HT) and poly(9,9-dioctylfluorene) (PF) and all-conjugated block-copolymers of them is presented. Moreover, the sequence of monomer addition in the synthesis of these conjugated block-copolymers is unimportant, which is unique. (C) 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 49: 5339-5349, 2011status: publishe