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| 2. |
- Cederholm, Linnea, et al.
(author)
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Chemical recycling to monomer: thermodynamic and kinetic control of the ring-closing depolymerization of aliphatic polyesters and polycarbonates
- 2023
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In: Polymer Chemistry. - : Royal Society of Chemistry (RSC). - 1759-9954 .- 1759-9962. ; 14:28, s. 3270-3276
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Journal article (peer-reviewed)abstract
- The thermodynamic equilibrium between ring-opening polymerization and ring-closing depolymerization is influenced by monomer-solvent-polymer interactions, an effect that can be utilized to promote chemical recycling to monomer. Here, the influence of monomer structure on this solvent effect has been investigated, showing that the chemical structure of the monomer influences the power of the solvent to supress the ceiling temperature. The study also demonstrates how catalyst selectivity can be utilized to obtain selective ring-closing depolymerization of one component of a polymer blend, even when the thermodynamics dictate otherwise.
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| 3. |
- Cederholm, Linnea, et al.
(author)
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Design for Recycling : Polyester- and Polycarbonate-Based A-B-A Block Copolymers and Their Recyclability Back to Monomers
- 2023
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In: Macromolecules. - : American Chemical Society (ACS). - 0024-9297 .- 1520-5835. ; 56:10, s. 3641-3649
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Journal article (peer-reviewed)abstract
- Chemical recycling to monomers (CRMs) of A-B-Ablockcopolymers is governed by the chemical structure and thereby the thermodynamicbehavior of different block constituents. Here, we show how a thermodynamictoolkit based on a cyclic monomer structure and solvent propertiescan be utilized in the design of recyclable A-B-A blockcopolymers with varying material properties. By combining four cyclicmonomers lactide, epsilon-decalactone, 2,2-diethyltrimethylene carbonate,and trimethylene carbonate, three different block copolymers werecreated, suitable for different CRM scenarios. The chemical structureof the soft midblock (epsilon-decalactone or trimethylene carbonate)appeared to have a critical impact both on the ring-closing depolymerizationbehavior and mechanical properties, where changing from a polyesterto a polycarbonate soft block increased Young's modulus from14 to 200 MPa. Hence, this work demonstrates the complexity as wellas the opportunities in the design of macromolecular structures fora circular economy.
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| 4. |
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| 5. |
- Cederholm, Linnea, et al.
(author)
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“Like Recycles Like” : Selective Ring-Closing Depolymerization of Poly(L-Lactic Acid) to L-Lactide
- 2022
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In: Angewandte Chemie International Edition. - : Wiley. - 1433-7851 .- 1521-3773. ; 61:33
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Journal article (peer-reviewed)abstract
- Chemical recycling of poly(L-lactic acid) to the cyclic monomer L-lactide is hampered by low selectivity and by epimerization and elimination reactions, impeding its use on a large scale. The high number of side reactions originates from the high ceiling temperature (Tc) of L-lactide, which necessitates high temperatures or multistep reactions to achieve recycling to L-lactide. To circumvent this issue, we utilized the impact of solvent interactions on the monomer–polymer equilibrium to decrease the Tc of L-lactide. Analyzing the observed Tc in different solvents in relation to their Hildebrand solubility parameter revealed a “like recycles like” relationship. The decreased Tc, obtained by selecting solvents that interact strongly with the monomer (dimethyl formamide or the green solvent γ-valerolactone), allowed chemical recycling of high-molecular-weight poly(L-lactic acid) directly to L-lactide, within 1–4 h at 140 °C, with >95 % conversion and 98–99 % selectivity. Recycled L-lactide was isolated and repolymerized with high control over molecular weight and dispersity, closing the polymer loop.
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| 6. |
- Cederholm, Linnea, et al.
(author)
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Microwave processing of lignin in green solvents : A high-yield process to narrow-dispersity oligomers
- 2020
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In: Industrial crops and products (Print). - : Elsevier BV. - 0926-6690 .- 1872-633X. ; 145
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Journal article (peer-reviewed)abstract
- Functional narrow-dispersity kraft lignin oligomers in high-yields were produced by a combined microwave-assisted extraction/degradation process. The process took place under mild non-catalytic conditions, in green solvents, and moderate temperatures (80 -160 degrees C). High yields, i.e., 63 % and 64 %, of lignin oligomers with narrow dispersity were obtained after only 40 min microwave processing in methanol and ethanol, respectively. The ethanol-soluble yield increased substantially after microwave processing as compared to samples extracted by liquid-solid solvent-extraction. This increase was mainly ascribed to the cleavage of beta-O-4 linkages, as indicated by semiquantitative 2D-HSQC NMR. Under the corresponding conditions in methanol, the yields after microwave processing were similar to those obtained by liquid-solid solvent-extraction. The difference is likely ascribed to the different reactivities of the solvents as O-alkylation agents. Furthermore, the obtained lignin fractions had high functionality, as shown by hydroxyl-group quantification through P-31-NMR. This, along with the narrow dispersity and rich aromatic structure, makes these oligomers interesting precursors for future thermoset syntheses.
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| 7. |
- Cederholm, Linnea
(author)
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Thermodynamic Toolkit for Chemical Recycling to Monomer
- 2023
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Doctoral thesis (other academic/artistic)abstract
- The design of polymeric materials for a circular economy is, to a largeextent, a challenge of thermodynamics. The work presented in this thesishas explored the thermodynamic features of ring-opening polymerizationand ring-closing depolymerization, to develop polymeric materials andrecycling strategies for chemical recycling to monomer.First, statistical copolymerization was explored as a tool for internal endcapping,in order to enhance the thermodynamic stability of an aliphaticpolyester. However, a drawback of the improved thermodynamic stabilitywas a negative impact on the recyclability. Next, the solvents effect on thethermodynamic equilibrium was studied. It was found that, apart from thedecreasing effect that dilution had on the ceiling temperature as aconsequence of the increased entropy, the properties of the solventstrongly influenced the equilibrium. This was studied for three differentsix-membered cyclic monomers, two lactones and one carbonate, whereceiling temperature of the more polar monomers where more influencedby the solvent effect. This solvent effect was used to realize chemicalrecycling to monomer of polylactide via ring-closing depolymerization,with high conversion and high selectivity. Finally, three different A–B–Atype block copolymers were designed. The influence of block componentson the mechanical properties and recyclability was investigated, showingthat the midblock chemical structure had a strong impact on the Young’smodulus, the elongation at break, as well as the on the ring-closingdepolymerization behavior.
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| 8. |
- Cederholm, Linnea, et al.
(author)
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Turning natural delta-lactones to thermodynamically stable polymers with triggered recyclability
- 2020
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In: Polymer Chemistry. - : ROYAL SOC CHEMISTRY. - 1759-9954 .- 1759-9962. ; 11:30, s. 4883-4894
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Journal article (peer-reviewed)abstract
- To extend the use of naturally occurring substituted delta-lactones within the polymer field, their commonly low ceiling temperature and thereby challenging equilibrium behavior needs to be addressed. A synthetic strategy to control the polymerization thermodynamics was therefore developed. This was achieved by copolymerizing delta-decalactone (delta DL) with either epsilon-decalactone (epsilon DL) or epsilon-caprolactone (epsilon CL) at room temperature (RT), with diphenyl phosphate (DPP) as catalyst. The thermodynamic stability of P delta DL-co-epsilon DL and P delta DL-co-epsilon CL increased with increased comonomer ratio in the feed, to 10% and 30% monomeric epsilon DL, respectively, at 110 degrees C. This is in contrast to the P delta DL homopolymer, which under the same conditions depolymerized to 70% monomeric delta DL at equilibrium. The copolymers' macromolecular structure, originating from the copolymerization kinetics, was found to be the crucial factor to mitigate delta DLs equilibrium behavior. To close the loop, designing materials for a circular economy, the recycling of P delta DL-co-epsilon DL was demonstrated, by reaction with benzyl alcohol (BnOH) as an external nucleophile, leading to cyclic monomers or dimers with BnOH at high yield.
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| 9. |
- McGivney, Eric, et al.
(author)
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Rapid Physicochemical Changes in Microplastic Induced by Biofilm Formation
- 2020
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In: Frontiers in Bioengineering and Biotechnology. - : Frontiers Media SA. - 2296-4185. ; 8
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Journal article (peer-reviewed)abstract
- Risk assessment of microplastic (MP) pollution requires understanding biodegradation processes and related changes in polymer properties. In the environment, there are two-way interactions between the MP properties and biofilm communities: (i) microorganisms may prefer some surfaces, and (ii) MP surface properties change during the colonization and weathering. In a 2-week experiment, we studied these interactions using three model plastic beads (polyethylene [PE], polypropylene [PP], and polystyrene [PS]) exposed to ambient bacterioplankton assemblage from the Baltic Sea; the control beads were exposed to bacteria-free water. For each polymer, the physicochemical properties (compression, crystallinity, surface chemistry, hydrophobicity, and surface topography) were compared before and after exposure under controlled laboratory conditions. Furthermore, we characterized the bacterial communities on the MP surfaces using 16S rRNA gene sequencing and correlated community diversity to the physicochemical properties of the MP. Significant changes in PE crystallinity, PP stiffness, and PS maximum compression were observed as a result of exposure to bacteria. Moreover, there were significant correlations between bacterial diversity and some physicochemical characteristics (crystallinity, stiffness, and surface roughness). These changes coincided with variation in the relative abundance of unique OTUs, mostly related to the PE samples having significantly higher contribution of Sphingobium, Novosphingobium, and uncultured Planctomycetaceae compared to the other test materials, whereas PP and PS samples had significantly higher abundance of Sphingobacteriales and Alphaproteobacteria, indicating possible involvement of these taxa in the initial biodegradation steps. Our findings demonstrate measurable signs of MP weathering under short-term exposure to environmentally relevant microbial communities at conditions resembling those in the water column. A systematic approach for the characterization of the biodegrading capacity in different systems will improve the risk assessment of plastic litter in aquatic environments.
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