| 1. |
- Claudino, Mauro, et al.
(författare)
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Bringing D-limonene to the scene of bio-based thermoset coatings via free-radical thiol-ene chemistry : macromonomer synthesis, UV-curing and thermo-mechanical characterization
- 2014
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Ingår i: Polymer Chemistry. - : Royal Society of Chemistry (RSC). - 1759-9954. ; 5:9, s. 3245-3260
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Tidskriftsartikel (refereegranskat)abstract
- The increasing pursuit for bio-based plastic materials led us to investigate the potential use of the monoterpene limonene in thermoset synthesis using the free-radical mediated thiol-ene reaction. The high efficiency of this reaction to prepare multifunctional ene-terminated resins, as intermediary macromolecular precursors, for thermosets synthesis was demonstrated under thermal and photoinitiated conditions. Although an excess of terpene favors formation of well-defined macromonomers in organic solution, the characteristic low-vapor pressure of limonene hinders its simple removal (or recycling) via evaporation after synthesis. Alteration to an initial thiol-ene stoichiometry of 1 : 0.5 enables production of high molecular weight resins in the form of 'hyperbranched oligomeric-like' structures having moderate polydispersity. UV-curing of these polyfunctional resins combined with equal mole compositions of multifunctional alkyl ester 3-mercapto propionates yields highly sticky, amorphous and flexible elastomers with different thermo-mechanical properties. These can be further modulated by varying the amount of unreacted thiol occluded within the networks working as a plasticizer. Introduction of a renewable cycloaliphatic structure into the materials offers a convenient way to enhance the glass-transition temperature and stiffness of traditional thiol-ene networks. The materials synthesized may be considered potentially useful as sealants and adhesives in a wide variety of applications including organic coatings. The versatility of UV-irradiation over thermal initiation makes this method particularly suitable for green industrial synthesis processes via thiol-ene chemistry using limonene and multifunctional thiols. The thiol-ene system evaluated herein serves as a model example for the sustainable incorporation of natural diolefinic monomers into semisynthetic thiol-ene networks exhibiting a range of thermo-mechanical properties.
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| 2. |
- Claudino, Mauro, 1977-
(författare)
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Macromolecular design : UV-curable thiol-ene networks based on renewable resources
- 2013
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Plant oils and terpenes are ubiquitous natural renewable compounds. The double bonds contained in most of these monomers can be utilized via the photo-induced free-radical thiol–ene reaction to create novel bio-derived polymer thermosets representing a valuable ‘green’ alternative to petrochemical olefins and resulting synthetic plastic materials. Nevertheless, there are several factors limiting their applicability, the first one being the relatively slow reaction rates towards thiol–ene coupling and many times the need to modify these natural olefins to make them more reactive. The latter process necessarily introduces additional pre-synthesis steps which has implications related both to cost and synthetic routes employed thereafter, those of which may or may not follow the principles of Green Chemistry. Therefore, this thesis intends to gain primary insight about the thiol–ene mechanism, kinetics and reactivity involving these multi-substituted olefins and then use the resulting knowledge to design semi-synthetic thermosets by incorporating these natural monomers into thiol–ene networks in the most environmentally friendly way possible. Mechanistic kinetic results show that internal 1,2-disubstituted enes found in mono-unsaturated vegetable oils and some macrolactones undergo a fast reversible cis/trans-isomerization process in favour of trans-isomer formation coupled with the thiol–ene mechanism. The slow reactivity of these enes has been accredited not just to the isomerization itself, but predominantly to the chain-transfer hydrogen-abstraction step. This rate-limiting step, however, does not seem to compromise their use in the creation of thiol–ene networks as demonstrated by photopolymerization in the melt of a series of linear globalide/ε-caprolactone-based copolyesters differing in amount of unsaturations along the backbone crosslinked with a tri-functional thiol propionate ester monomer. The resulting thermoset films were amorphous elastomers exhibiting different thermal and mechanical properties depending on the comonomer feed ratio. D-limonene, a renewable diolefinic substrate, proved to be an important terpene in free-radical thiol–ene additions. Empirical results show that the 1,1-disubstituted exo-vinylidene bond is about 6.5 times more reactive than the endocyclic 1,1,2-trisubstituted 1-methyl-cyclohexene moiety when reacting with mercapto propionate esters in organic solution conditions. Kinetic modeling results suggest that the differences in double bond reactivity are partially ascribed to steric impediments coupled with differences in electron-density controlling thiyl-radical insertion onto the two unsaturations but predominantly to differences in relative energy between the two tertiary insertion carbon-centered radical intermediates. Off-stoichiometric manipulations in the thiol–limonene mole ratio, assisted by numerical model simulations, offer a convenient method to visualize and assess the overall reaction system kinetics irrespective of time, thus being regarded as an important guiding tool for organic and polymer chemists aiming at designing thiol–ene reaction systems based on limonene. Multifunctional limonene-terminated thiol–ene macromonomer resins were synthesized in ethyl acetate solution and then reacted in different combinations with polyfunctional mercapto propionate esters to afford semi-synthetic thiol–ene networks with different thermo-viscoelastic properties depending on functionality, crosslink density, homogeneity and excess ofthiol occluded into the networks. The bulky cycloaliphatic ring structure of limonene locked between thioether linkages introduce a certain degree of rigidity to the final networks and increase the glass-transition temperature when compared tomore standard thiol–allyl systems. In all cases evaluated, high thiol–ene conversions were achieved with minimum or no side-reactions such as chain-growth homopolymerization and at reasonable reaction rates.
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| 3. |
- Claudino, Mauro, et al.
(författare)
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Photoinduced thiol-ene cross-linking of globalide/ε-caprolactone copolymers : curing performance and resulting thermoset properties
- 2012
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Ingår i: Journal of Polymer Science Part A. - : Wiley. - 0887-624X .- 1099-0518. ; 50:1, s. 16-24
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Tidskriftsartikel (refereegranskat)abstract
- The increasing demand for bioderived polymers led us to investigate the potential use of the macrolactone globalide in thermoset synthesis via the photoinduced thiolene reaction. A series of six lipase-catalyzed poly(globalide-caprolactone) copolyesters bearing internal main-chain unsaturations ranging from 10 to 50 and 100 mol % were successfully crosslinked in the melt with equal amounts of thiol groups from trimethylolpropane-trimercapto propionate affording fully transparent amorphous elastomeric materials with different thermal and viscoelastic properties. Three major conclusions can be drawn from this study: (i) high thiol-ene conversions (> 80%) were easily attained for all cases, while maintaining the cure behavior, and irrespective of functionality at reasonable reaction rates; (ii) parallel chain-growth homopropagation of the ene monomer is insignificant when compared with the main thiolene coupling route; and (iii) high ene-density copolymers result in much lower extracted sol fractions and high T(g) values as a result of a more dense and homogeneous crosslinked network. The thiol-ene system evaluated in this contribution serve as model example for the sustainable use of naturally occurring 1,2-disubstituted alkenes in making semisynthetic polymeric materials in high conversions with a range of properties.
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| 4. |
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| 5. |
- Claudino, Mauro, et al.
(författare)
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Thiol-ene coupling kinetics of D-limonene : a versatile 'non-click' free-radical reaction involving a natural terpene
- 2013
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Ingår i: RSC Advances. - : RSC Publishing. - 2046-2069. ; 3:27, s. 11021-11034
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Tidskriftsartikel (refereegranskat)abstract
- The free-radical photoinduced thiol-ene reaction between D-limonene, as renewable diolefinic substrate, and two mono-/tri-functional thiols (iso-tridecyl 3-mercaptopropionate and trimethylolpropane tris(3-mercaptopropionate)), has been investigated kinetically to define a relationship between alkene structure and reactivity. Separate thiol-ene solutions of the appropriate thiol in d-chloroform, supplemented with 1.0 wt% of DMPA (Irgacure 651), were subjected to polychromatic UV-irradiation and the chemical changes monitored discontinuously via H-1 NMR spectroscopy to quantify double bond conversion. The kinetic concentration profiles were modeled analytically and simulated in the application software COPASI for parameter estimation and to verify if the experimental data explained a suggested mechanistic scheme. Empirical results demonstrate that the external vinylidene bond of limonene reacts about 6.5 times faster with thiol than the internal trisubstituted 1-methyl-cyclohexene unsaturation. The selectivity observed for the two unsaturations was successfully explained by means of a simplified steady-state equation derived from the sequential reaction mechanism accounting for propagation and chain-transfer elementary steps with estimated rate coefficients. Kinetic modeling results attribute the difference in selectivity partially to steric impediments controlling thiyl-radical insertion onto the double bonds and predominantly to differences in relative energy between the two tertiary insertion carbon radical intermediates. The rate-limiting step was identified as the third chain-transfer hydrogen-abstraction reaction promoted by the second insertion carbon radical intermediate. High thiol-ene conversions were obtained in a timely fashion without major influence of secondary reactions demonstrating the suitability of this reaction for network forming purposes. The mechanistic and kinetic information collected can be used as a quantitative predictive tool to assess the potential use of D-limonene in thiol-ene network forming systems involving multifunctional alkyl ester 3-mercaptopropionates.
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| 6. |
- Claudino, Mauro, et al.
(författare)
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Thiol-ene coupling of 1,2-disubstituted alkene monomers : The kinetic effect of cis/trans-isomer structures
- 2010
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Ingår i: European Polymer Journal. - : Elsevier BV. - 0014-3057 .- 1873-1945. ; 46:12, s. 2321-2332
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Tidskriftsartikel (refereegranskat)abstract
- The free-radical induced reaction between a tri-functional thiol (2-ethyl-(hydroxymethyl)-1,3-propanediol trimercapto propionate) and two 1,2-disubstituted alkenes (methyl oleate and methyl elaidate) has been investigated under photochemical conditions. The photoreaction was monitored via time-resolved FUR, Raman and NMR spectroscopy to provide insights about the kinetics and efficiency in end-product formation. The information collected was subjected to numerical modelling using the GEPASI software using pre-established literature values for the rate coefficients in order to verify the proposed reaction scheme. The results confirm the thiol-ene reaction mechanism showing a very fast cis/trans-isomerization (<1.0 min) when compared with the total disappearance of unsaturations, indicating that the rate-limiting step controlling the reaction is the hydrogen transfer from the thiol involved in the formation of product. High thiol-ene conversions can be obtained at reasonable rates without major influence of side-reactions when performed in bulk indicating that this reaction is suitable for network forming purposes with mono-unsaturated fatty acid methyl esters derivatives. The kinetic and mechanistic information collected provides a basis for the design of new thiol-ene systems aiming at material and coating applications.
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| 7. |
- Claudino, Mauro
(författare)
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Thiol−ene Coupling of Renewable Monomers : at the forefront of bio-based polymeric materials
- 2011
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Plant derived oils bear intrinsic double-bond functionality that can be utilized directly for the thiol–ene reaction. Although terminal unsaturations are far more reactive than internal ones, studies on the reversible addition of thiyl radicals to 1,2-disubstituted alkenes show that this is an important reaction. To investigate the thiol–ene coupling reaction involving these enes, stoichiometric mixtures of a trifunctional propionate thiol with monounsaturated fatty acid methyl esters (methyl oleate or methyl elaidate) supplemented with 2.0 wt.% Irgacure 184 were subjected to 365-nm UV-irradiation and the chemical changes monitored. Continuous (RT– FTIR) and discontinuous (NMR and FT–Raman) techniques were used to follow the progress of the reaction and reveal details of the products formed. Experimental results supported by numerical kinetic simulations of the system confirm the reaction mechanism showing a very fast cis/trans-isomerization of the alkene monomers (<1.0 min) when compared to the total disappearance of double-bonds, indicating that the rate-limiting step controlling the overall reaction is the hydrogen transfer from the thiol involved in the formation of final product. The loss of total unsaturations equals thiol consumption throughout the entire reaction; although product formation is strongly favoured directly from the trans-ene. This indicates that initial cis/trans-isomer structures affect the kinetics. High thiol–ene conversions could be easily obtained at reasonable rates without major influence of side-reactions demonstrating the suitability of this reaction for network forming purposes from 1,2-disubstituted alkenes. To further illustrate the validity of this concept in the formation of cross-linked thiol–ene films a series of globalide/caprolactone based copolyesters differing in degree of unsaturations along the backbone were photopolymerized in the melt with the same trithiol giving amorphous elastomeric materials with different thermal and viscoelastic properties. High thiol–ene conversions (>80%) were easily attained for all cases at reasonable reaction rates, while maintaining the cure behaviour and independent of functionality. Parallel chain-growth ene homopolymerization was considered negligible when compared with the main coupling route. However, the comonomer feed ratio had impact on the thermoset properties with high ene-density copolymers giving networks with higher glass transition temperature values (Tg) and a narrower distribution of cross-links than films with lower ene composition. The thiol–ene systems evaluated in this study serve as model example for the sustainable use of naturally-occurring 1,2-disubstituted alkenes at making semi-synthetic polymeric materials in high conversions with a range of properties in an environment-friendly way.
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| 8. |
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| 9. |
- Claudino, Mauro, et al.
(författare)
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Utilizing thiol-ene coupling kinetics in the design of renewable thermoset resins based on D-limonene and polyfunctional thiols
- 2014
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Ingår i: RSC Advances. - : Royal Society of Chemistry (RSC). - 2046-2069. ; 4:20, s. 10317-10329
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Tidskriftsartikel (refereegranskat)abstract
- An extended model is developed to predict the free-radical thiol-ene reaction dynamics between D-limonene, as a renewable diolefin, and a monothiol compound (iso-tridecyl 3-mercaptopropionate) in bulk liquid conditions. Thermally and photo-initiated reactions of the two monomers showed favored thiol-ene coupling at the exo-isopropenyl alkene structure when reacted at 1 : 1 and 1 : 0.5 mole ratios. Experimental kinetic data obtained from the two stoichiometries were well reproduced numerically via the simulation software COPASI by introducing a multi-route mechanistic scheme with propagation-chain-transfer steps accounting for primary (mono-additions) and secondary (di-addition) modes of coupling. The differences in intrinsic double-bond reactivity enable synthesis of limonene-terminated resins (mono-versus poly-disperse) as multifunctional network precursors. Off-stoichiometry manipulations in the initial mole ratio, assisted by numerical simulations, offer a convenient approach to visualize the overall reaction system kinetics irrespective of temporal effects, thus being regarded as an important guiding tool for chemists aiming at designing thiol-ene systems based on limonene.
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| 10. |
- Finnveden, Maja, 1986-, et al.
(författare)
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Lipase-Catalyzed Synthesis of Renewable Plant Oil-Based Polyamides.
- 2019
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Ingår i: Polymers. - : MDPI. - 2073-4360. ; 11:11
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Tidskriftsartikel (refereegranskat)abstract
- Enzyme catalyzed synthesis of renewable polyamides was investigated using Candida antarctica lipase B. A fatty acid-derived AB-type functional monomer, having one amine and one methyl ester functionality, was homopolymerized at 80 and 140 °C. Additionally, the organobase 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) was used as a catalyst. The results from the two catalysts were comparable. However, the amount of lipase added was 1.2 × 103 times lower, showing that the lipase was a more efficient catalyst for this system as compared to TBD. Moreover, the AB-type monomer was copolymerized with 1,12-diaminododecane to synthesize oligoamides of two different lengths.
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