Abstract:A detailed overview is given on the currently developed analytical and advanced kinetic models to calculate the main bulk/solution chain-growth copolymerization characteristics.
“…4b, c. Figure 4a shows that for both the 10 and 50 mol % initial functionality loading the well-known terminal Mayo-Lewis 41,42 behavior is followed:Fig. 4Conventional analysis of 2-oxazoline comonomer incorporation.…”
Section: Resultsmentioning
confidence: 95%
“…Conventional analysis of the comonomer incorporation in a copolymerization process focuses in addition mostly on the instantaneous average copolymer composition F A,inst 42 , which reflects the average amount of comonomer A incorporated in all active chains at a certain moment for a given molar fraction of A in the reaction mixture ( f A ).…”
Even though functional copolymers with a low percentage of functional comonomer units (up to 20 mol%) are widely used, for instance for the development of polymer therapeutics and hydrogels, insights in the functional group distribution over the actual chains are lacking and the average composition is conventionally used to describe the functionalization degree. Here we report the visualization of the monomer distribution over the different polymer chains by a synergetic combination of experimental and theoretical analysis aiming at the construction of functionality-chain length distributions (FUNC-CLDs). A successful design of the chemical structure of the comonomer pair, the initial functional comonomer amount (13 mol%), and the temperature (100 °C) is performed to tune the FUNC-CLD of copoly(2-oxazoline)s toward high functionalization degree for both low (100) and high (400) target degrees of polymerization. The proposed research strategy is generic and extendable to a broad range of copolymerization chemistries, including reversible deactivation radical polymerization.
“…4b, c. Figure 4a shows that for both the 10 and 50 mol % initial functionality loading the well-known terminal Mayo-Lewis 41,42 behavior is followed:Fig. 4Conventional analysis of 2-oxazoline comonomer incorporation.…”
Section: Resultsmentioning
confidence: 95%
“…Conventional analysis of the comonomer incorporation in a copolymerization process focuses in addition mostly on the instantaneous average copolymer composition F A,inst 42 , which reflects the average amount of comonomer A incorporated in all active chains at a certain moment for a given molar fraction of A in the reaction mixture ( f A ).…”
Even though functional copolymers with a low percentage of functional comonomer units (up to 20 mol%) are widely used, for instance for the development of polymer therapeutics and hydrogels, insights in the functional group distribution over the actual chains are lacking and the average composition is conventionally used to describe the functionalization degree. Here we report the visualization of the monomer distribution over the different polymer chains by a synergetic combination of experimental and theoretical analysis aiming at the construction of functionality-chain length distributions (FUNC-CLDs). A successful design of the chemical structure of the comonomer pair, the initial functional comonomer amount (13 mol%), and the temperature (100 °C) is performed to tune the FUNC-CLD of copoly(2-oxazoline)s toward high functionalization degree for both low (100) and high (400) target degrees of polymerization. The proposed research strategy is generic and extendable to a broad range of copolymerization chemistries, including reversible deactivation radical polymerization.
“…As in many theoretical derivations, in several fields one can opt to describe a certain phenomenon in a differential or integral manner. [152,153] In the present section, we put forward the most important continuum-based integral constitutive models. To predict the viscoelastic deformation behavior at the nonlinear strain region, the single integral K-BKZ constitutive model, as first proposed 50 years ago, [154][155][156] is often used.…”
Section: Continuum-based Integral Constitutive Modelsmentioning
Exit velocity profiles for parallel die and die optimized using conical widening or narrowing. Reproduced permission. [164] Copyright 2010, Elsevier Ltd. c) Average velocity of each outflow subsection of the slit die (width = 100 mm and height = 1.5 mm), Reproduced with permission. [173] Copyright 2012, Elsevier Ltd. d,e) The geometry profiles of the Catheter cross section covered as case study. f) The velocity distribution at the die outflow for different trials-T0: the original die profile; T1: r 2 varies from 0.9 to 0.95 mm; T2: r 2 varies from 0.95 to 0.9 mm, θ 2 varies from 45° to 43°; T3: r 2 varies from 0.9 to 0.95 mm; T4: θ 2 varies from 43° to 40°; T5: r 3 varies from 0.7 to 0.65 mm. Reproduced with permission. [166] Copyright 2013, Elsevier. g) The corresponding objective function evolution in consecutive trials. Reproduced with permission. [166] Copyright 2013, Elsevier Ltd.
“…In practice, it is advisable to identify the most dominant reaction steps, taking into account that more recent research has indicated the relevance of penultimate monomer unit (PMU) effects as well [66]. This implies that, to describe the reactivity of a macroradical, one should potentially also consider the monomer unit preceding the unit containing the radical center (the so-called penultimate monomer unit), instead of a conventional approach focusing only on the terminal monomer unit: hence, the unit with the radical center [67][68][69].…”
Section: Radical Reaction Mechanisms For Thermal Pmma Chemical Recyclingmentioning
Chemical or feedstock recycling of poly(methyl methacrylate) (PMMA) by thermal degradation is an important societal challenge to enable polymer circularity. The annual PMMA world production capacity is over 2.4 × 106 tons, but currently only 3.0 × 104 tons are collected and recycled in Europe each year. Despite the rather simple chemical structure of MMA, a debate still exists on the possible PMMA degradation mechanisms and only basic batch and continuous reactor technologies have been developed, without significant knowledge of the decomposition chemistry or the multiphase nature of the reaction mixture. It is demonstrated in this review that it is essential to link PMMA thermochemical recycling with the PMMA synthesis as certain structural defects from the synthesis step are affecting the nature and relevance of the subsequent degradation reaction mechanisms. Here, random fission plays a key role, specifically for PMMA made by anionic polymerization. It is further highlighted that kinetic modeling tools are useful to further unravel the dominant PMMA degradation mechanisms. A novel distinction is made between global conversion or average chain length models, on the one hand, and elementary reaction step-based models on the other hand. It is put forward that only by the dedicated development of the latter models, the temporal evolution of degradation product spectra under specific chemical recycling conditions will become possible, making reactor design no longer an art but a science.
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