A statistical theory of polymer network degradation

Pierre, Guillaume; Richaud, Emmanuel; Verdú, J.

doi:10.1016/j.polymer.2014.05.008

Cited by 16 publications

(12 citation statements)

References 26 publications

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“…Thus, depolymerization of unprocessed lignin remains of significant interest 8,16 and has been pursued experimentally with polyoxometalate catalysts 17 , base-catalyzed hydrolysis [18][19] , acidolysis [20][21] , ionic liquid treatment 22 , reduction with hydrosilanes 23 , photochemical degradation 24 , and ball milling 25 . In addition to general depolymerization, efforts have also included selective strategies via homogeneous catalysts [26][27][28][29][30] and enzymes 31 .…”

Section: Introductionmentioning

confidence: 99%

Depolymerization Pathways for Branching Lignin Spirodienone Units Revealed with ab Initio Steered Molecular Dynamics

Mar

Kulik

2017

J. Phys. Chem. A

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Lignocellulosic biomass is an abundant, rich source of aromatic compounds, but direct utilization of raw lignin has been hampered by both the high heterogeneity and variability of linking bonds in this biopolymer. Ab initio steered molecular dynamics (AISMD) has emerged both as a fruitful direct computational screening approach to identify products that occur through mechanical depolymerization (i.e., in sonication or ball-milling) and as a sampling approach. By varying the direction of force and sampling over 750 AISMD trajectories, we identify numerous possible pathways through which lignin depolymerization may occur in pyrolysis or through catalytic depolymerization as well. Here, we present eight unique major depolymerization pathways discovered via AISMD for the recently characterized spirodienone lignin branchinglinkage that may comprise around 10% weight of all lignin in some softwoods. We extract representative trajectories from AISMD and carry out reaction pathway analysis to identify energetically favorable pathways for lignin depolymerization. Importantly, we identify dynamical effects that could not be observed through more traditional calculations of bond dissociation energies. Such effects include thermodynamically favorable recovery of aromaticity in the dienone ring that leads to near-barrierless subsequent ether cleavage and hydrogen bonding effects that stabilize newly formed radicals. Some of the most stable spirodienone fragments that reside at most 1 eV above the reactant structure are formed with only 2 eV barriers for C-C bond cleavage, suggesting key targets for catalyst design to drive targeted depolymerization of lignin.2

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Section: Introductionmentioning

confidence: 99%

Depolymerization Pathways for Branching Lignin Spirodienone Units Revealed with ab Initio Steered Molecular Dynamics

Mar

Kulik

2017

J. Phys. Chem. A

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“…The value of glass transition is thus a reliable indicator of the ageing effects in UDMA networks. In the case of UDMA based dental materials, in addition to the thermally induced reactions discussed in this paper, the T g changes can either originate from structural relaxation [37] (with a T g increase), or water diffusion (with a T g decrease) [38], with a possible interplay between them [39], or chemical degradation involving the hydrolysis of urethane [40] or ester functions [41] leading to T g decrease [ 26 ] and at very long term the total destruction of network (also named "degelation" [42]).…”

Section: Discussionmentioning

confidence: 99%

Curing of urethane dimetracrylate composites: A glass transition study

Nguyen

Pomès

Sadoun³

et al. 2019

Polymer Testing

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Urethane dimethacrylate thermosets (UDMA) and their composites (PICN) were cured under varying polymerization pressures (1-3500 bars) and the resulting materials were characterized mainly by dynamic mechanical analysis (DMA) to measure their glass transition. In the case of PICN, glass transition displays an optimum in the middle pressure range (1000-2000 bars), which is linked to the conversion degree of polymerization process as measured by near infrared (NIR) spectrometry whereas it displays hyperbolic increase for UDMA networks. The results were discussed using classical theories used for describing the glass transition of networks. For samples post-cured at 160 � C during 1 h, the glass transition of undercured samples (1-1000 bars and P > 3000 bars) is shown to increase in link with possible post-curing. Reversely, the T g of the most cured samples (polymerization pressure about 2000 bars) decreases which was attributed to the possible thermal decomposition. The glass transition temperature is here tentatively proposed a marker of the network architecture for samples varying by their processing (curing, post-curing) conditions and possibly their degradation level.

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“…the critical stage at which chain scissions have cleared out all the elastically active chains and the network reverts back to a soluble material (with the possibility to regenerate chemicals and repolymerize them later). An original approach for predicting the degelation was developed by Gilormini et al [40]: in the simplest version of this approach, a chain contains L reactive groups likely to undergo a chain scission process.…”

Section: Study Of Degradation At Macromolecular Scalementioning

confidence: 99%

“…The author wants to express his sincere gratitude to Dr. Pierre Gilormini for his collaboration on degradation in polymers networks (Refs [21,40,41]). Besides his innovative approaches, Pierre is always a very accessible colleague, and is an example of rigor and curiosity who has inspired many young researchers in PIMM.…”

Section: Acknowledgementsmentioning

confidence: 99%