Ricardo Ortiz - Academia.edu (original) (raw)

Papers by Ricardo Ortiz

Research paper thumbnail of Synthesis of Activated Monomers for Cationic Photopolymerization

Journal of Macromolecular Science, Part A, 2004

A series of novel cationically photopolymerizable epoxide and vinyl ether monomers bearing substi... more A series of novel cationically photopolymerizable epoxide and vinyl ether monomers bearing substituted benzyl ether groups were prepared. Monomers with one methoxy, methylenedioxy, and three methoxy groups on the aromatic ring of the benzyl ether group were synthesized by straightforward methods. Kinetic studies using real‐time infrared spectroscopy of the cationic photopolymerizations of these novel monomers showed that those monomers with

Research paper thumbnail of Synthesis of Novel Hexathiolated Squalene and Its Thiol-Ene Photopolymerization with Unsaturated Monomers

Green and Sustainable Chemistry, 2012

In this work is described the synthesis of a multifunctional thiolated squalene. Thiol-ene coupli... more In this work is described the synthesis of a multifunctional thiolated squalene. Thiol-ene coupling reactions were employed to functionalize the six double bonds of squalene, using thiolacetic acid. Hydrolysis of the resulting thioacetates, rendered the corresponding hexathiolated squalene SQ6SH. This compound was further photopolymerized separately with triallyl cyanurate, pentaerythritol triacrylate and diethyleneglycol divinyl ether. Real Time FTIR kinetics revealed that homopolymerization of the ene monomers took place in addition to the thiol-ene photopolymerization. Flexible films were obtained when SQ6SH was photopolymerized in bulk with the above mentioned unsaturated monomers.

Research paper thumbnail of Design and synthesis of highly reactive photopolymerizable epoxy monomers

Journal of Polymer Science Part A-polymer Chemistry, 2001

The synthesis of a series of novel cationically photopolymerizable epoxide monomers bearing benzy... more The synthesis of a series of novel cationically photopolymerizable epoxide monomers bearing benzyl, allyl, and propargyl acetal and ether groups that can stabilize free radicals was carried out. These monomers display enhanced reactivity in cationic photopolymerization in the presence of certain onium salt photoinitiators. Specifically, this article describes schemes for the synthesis of cycloaliphatic epoxy monomers bearing free-radical stabilizing groups. During UV irradiation of an onium salt cationic photoinitiator, the aryl radicals that are generated abstract labile protons present in such monomers to generate the corresponding carbon-centered radicals. Subsequently, these radicals can interact with the onium salt by a redox mechanism to induce the decomposition of these salts. The overall result is that additional cationic species are generated by this mechanism that increase the rate and extent of the cationic ring-opening polymerization of the epoxide monomer. An investigation of the photopolymerizations of the monomers prepared during this work was carried out using Fourier transform real-time infrared spectroscopy, and conclusions were drawn with respect to the relationship between their structures and reactivity. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2385–2395, 2001

Research paper thumbnail of Synthesis of epoxy monomers that undergo synergistic photopolymerization by a radical-induced cationic mechanism

Journal of Polymer Science Part A-polymer Chemistry, 2001

A series of novel, cycloaliphatic, cationically photopolymerizable epoxide monomers bearing benzy... more A series of novel, cycloaliphatic, cationically photopolymerizable epoxide monomers bearing benzyl ether groups were prepared. These monomers display a considerable enhancement in the rate of their cationic ring-opening polymerizations in comparison with monomers that do not contain such groups. In this article, a synergistic free-radical mechanism is proposed that accounts for this effect, and supporting evidence is offered for its verification. During UV irradiation of an onium salt cationic photoinitiator, the aryl radicals that are generated abstract labile benzyl hydrogens present in such monomers to generate the corresponding carbon-centered radicals. Subsequently, these radicals are oxidized to benzyl carbocations by the onium salt via a nonphotochemical chain process. The observed increase in the rate and extent of the cationic ring-opening polymerization of the epoxide monomers is due to the aforementioned mechanism, which effectively increases the number of reactive cationic species present during polymerization. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3578–3592, 2001

Research paper thumbnail of Benzyl alcohols as accelerators in the photoinitiated cationic polymerization of epoxide monomers

Journal of Polymer Science Part A-polymer Chemistry, 2002

Benzyl alcohols display marked accelerating effects on the onium salt photoinitiated cationic rin... more Benzyl alcohols display marked accelerating effects on the onium salt photoinitiated cationic ring-opening polymerizations of epoxide monomers. The participation of radicals in these polymerizations was demonstrated, and a pronounced accelerating effect on the polymerization rate was observed depending on the character of the substituent on the benzene ring of the alcohol. 4-Methoxybenzyl alcohol was considerably more reactive than benzyl alcohol, whereas the analogous chloro- and nitrosubstituted compounds were less reactive. Piperonyl alcohol was even more reactive as an accelerator in these polymerizations. The UV irradiation of an onium salt cationic photoinitiator generates Brönsted acids that initiate the cationic ring-opening polymerization of the epoxide monomer. In the presence of benzyl alcohol, the usual polymerization mechanism is diverted and proceeds by a more-rapid activated monomer mechanism. As a result, benzyl ether groups are incorporated at the termini of the polymer chains. Aryl radicals that are also generated by photolysis of the onium salt abstract labile benzyl ether protons, and the benzyl ether radicals that are produced are subsequently oxidized by the onium salt to afford the corresponding benzyl carbocations. This takes place by a chain process. The polymer bound benzyl cations serve as additional sites for the initiation of cationic polymerization. It is proposed that these two mechanisms acting in synergy with one another account for the observed accelerating effect on the polymerization rate. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2298–2309, 2002

Research paper thumbnail of Synthesis of a novel biopolymer by means of Thiol-Ene Photopolymerization using diallyl sucrose and dithiotreitol as comonomers

MRS Proceedings, 2010

ABSTRACT

Research paper thumbnail of Synthesis of novel highly reactive silicone-epoxy monomers for cationic photopolymerizations

Polymer, 2005

A series of novel cationically photopolymerizable silicone-epoxide monomers bearing substituted b... more A series of novel cationically photopolymerizable silicone-epoxide monomers bearing substituted benzyl ether groups were prepared. Monomers with methoxy groups on the aromatic ring of the benzyl ether group were synthesized by sequential hydrosylation reactions of 1,1,3,3-tetramethyl disiloxane. Kinetic studies using real-time infrared spectroscopy of the cationic photopolymerizations of these novel monomers showed that those monomers with methoxy groups exhibited elevated rates of photopolymerization. The acceleration effect was explained on the basis of synergistic effects of two mechanisms, namely, the normal ring opening polymerization catalyzed by a Brönstead acid, and the cationic photopolymerization induced by the redox interaction between the free radicals formed in the backbone of the monomer and the onium salt used as photoinitiator. The methoxy groups on the aromatic ring of the benzyl ether enhance the stabilization of the carbocation formed in the structure of the monomer. Silicone-epoxy monomer with 2,5-dimethoxybenzyl ether group exhibited the higher photopolymerization rate. The latter compound can also be used as accelerator of the cationic photopolymerization of commercial silicone-epoxy monomer when used in low concentrations.

Research paper thumbnail of Development and study of a coupling agent for photocurable hybrid thiol/ene/cationic formulations

Macromolecular …, 2008

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Research paper thumbnail of Interactions in the thermal and light stabilising action of novel aromatic phosphites with a 2-hydroxybenzophenone and hindered piperidine stabiliser in polyolefin …

Polymer degradation and stability, 1995

The interactions of two novel phosphite stabilisers with a commercial polymeric hindered piperidi... more The interactions of two novel phosphite stabilisers with a commercial polymeric hindered piperidine stabiliser, Chimassorb 944, and a 2-hydroxy-4-n-ctoxybenzophenone stabiliser, Cyasorb UV 531, have been examined in the thermal and photooxidation of polypropylene and high density polyethylene films using FTIR spectroscopy. The two structures are based on a bis-hindered phenolic moiety coupled to a 2-hydroxybenzophenone and a 4-amino-tetramethylpiperidine (3) chromophore.

Research paper thumbnail of Thermal and photostabilization behaviour of a novel naphthalene-HALS derivative in HDPE and PP films

Polymer degradation and …, 1999

A novel N-[-8-(2-naphthoxy)Octyl]-4-amino,2,2,6,6-tetramethylpiperidine stabiliser has been synth... more A novel N-[-8-(2-naphthoxy)Octyl]-4-amino,2,2,6,6-tetramethylpiperidine stabiliser has been synthesised and characterised and its thermal and photostabilising performance examined in both high density polyethylene and polypropylene ®lms. Its performance has been compared with that of a commercial hindered piperidine light stabiliser, Tinuvin 770 together with the eects of naphthalene. Using FTIR analysis, the naphthoxy-HALS showed excellent properties as a thermal and photostabiliser, showing strong autosynergism in the former case. Comparisons with Tinuvin 770, showed that the naphthalenic moiety of the molecule plays a role in the thermal stabilization process by scavenging oxygen. Naphthalene itself exhibited some degree of thermal stabilization and reversed its behaviour from being a weak stabilizer at low concentrations to a prooxidant at higher concentrations. The same pattern of stabilization was observed during the photoaging of polypropylene with the exception of the mixture of Tinuvin 770 and naphthalene which was found to exhibit the best performance at the higher concentration. #

Research paper thumbnail of Preparation of a crosslinked sucrose polymer by thiol–ene photopolymerization using dithiothreitol as comonomer

Carbohydrate Polymers, 2010

The thiol-ene photopolymerization technique was used to prepare a crosslinked sucrose polymer. Su... more The thiol-ene photopolymerization technique was used to prepare a crosslinked sucrose polymer. Sucrose was chemically modified to introduce two allyl groups, however, in the synthesis were also produced mono and triallyl derivatives. After purification by column chromatography, a fraction (F2A2S) with 94% diallyl sucrose (A2S), 4% of triallyl sucrose (A3S) and 2% of monoallyl sucrose (A1S) was obtained. This fraction was subsequently photopolymerized with dithiothreitol (DTT) which is a difunctional thiol. The presence of small concentration of A3S in F2A2S helped to crosslink in situ the obtained polythioether. Photopolymerization kinetics were determined using the Real-Time Infrared technique. It was found that photopolymerization can proceed in the absence of photoinitiators but the rate of photopolymerization and conversion increased considerably when different photoinitiators at 1 mol% were used and when the intensity of UV light was increased. The analysis by DMA of probes of the obtained sucrose polythioether revealed that the difunctionality of both comonomers, A2S and DTT, resulted in flexible materials with a T g of 30 • C and high storage modulus values. The sucrose polythioether was completely degraded in 2 h in strongly acidic medium. Additionally, the ability of water to absorb the prepared material was tested. We found that it was pH dependent with the maximum absorption at pH = 14. The biopolymer displayed high thermal stability up to 230 • C.

Research paper thumbnail of Effect of introducing a cationic system into a thiol‐ene photopolymerizable formulation

Journal of Polymer …, 2007

Hybrid materials derived from a thiol-ene and cationic polymerization were obtained from concomit... more Hybrid materials derived from a thiol-ene and cationic polymerization were obtained from concomitant polymerization. The hybrid materials were cured by both photopolymerization and thermally induced polymerization. The kinetics of the photopolymerization were measured using time resolved-IR and optical pyrometry. The nucleophilic character of the polysulfide obtained initially in the thiol-ene polymerization inhibited the development of the cationic photoinitiated polymerization of epoxy monomers. Besides, the epoxide groups underwent a proton catalyzed addition reaction with the thiols to form new sulfides groups in the reaction mixture. It is proposed that the formed sulfides can terminate the growing polyether chains forming dormant species like trialkylsulfonium salts. These salts promote the thermal polymerization of the epoxy monomer in a post treatment, producing hard and transparent materials. V V C 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4829-4843, 2007

Research paper thumbnail of Development of Hybrid Polymeric Materials Based on Thiol‐Ene/Cationic Formulations

Macromolecular …, 2008

Novel materials were prepared from dual photo and thermal polymerization of hybrid thiolene/catio... more Novel materials were prepared from dual photo and thermal polymerization of hybrid thiolene/cationic systems. In the first stage, the thiol-ene system proceeded to high conversions, while the cationic photopolymerization was inhibited. The formation of sulfides during this stage was the main factor for the inhibition of the cationic photopolymerization of the epoxy monomers. Once those sulfides were formed, they reacted with the oxonium-terminated growing polyether chains to form trialkylsulfonium salts. These salts promoted the thermal polymerization of the epoxy monomers in the second stage. The viscoelastic properties of the resulting polymers were measured by DMA.

Research paper thumbnail of Thermal and photo-oxidative stabilisation of polyolefin films: mode of action of novel naphthalene-hindered piperidine derivatives

Polymer degradation and stability, 1998

Research paper thumbnail of An effective method to prepare sucrose polymers by Thiol-Ene photopolymerization

Carbohydrate …, 2009

... a , E-mail The Corresponding Author , Aida E. Garcia Valdéz a , Marty Georgina Martinez Aguil... more ... a , E-mail The Corresponding Author , Aida E. Garcia Valdéz a , Marty Georgina Martinez Aguilar a and Maria Lydia Berlanga Duarte ... to prepare materials with potential applications as restorative dental resins (Carioscia, 2005; Lu, Carioscia, Stansbury, and Bowman, 2005) and ...

Research paper thumbnail of A kinetic study of the acceleration effect of substituted benzyl alcohols on the cationic photopolymerization rate of epoxidized natural oils

Polymer, 2005

The rate of the cationic photopolymerization of epoxidized natural oils was enhanced by the addit... more The rate of the cationic photopolymerization of epoxidized natural oils was enhanced by the addition of several mono, di and trisubstituted benzyl alcohols. The epoxidation of vegetable oils was achieved by using 30% hydrogen peroxide with methyl trioxo rhenium (MTO) as a phase transfer catalyst. Then, the effect of different methoxy-substituted benzyl alcohols on the curing rate was evaluated, using the real-time FT-IR technique. The overall result was an increase in the curing rate. The acceleration effect was explained on the basis of synergistic effects of two mechanisms, namely, the radical induced cationic photopolymerization and the activated monomer mechanism. Epoxidized oils with 2,5-dimethoxybenzyl alcohol as an accelerator exhibited the highest photopolymerization rate. Higher conversions were obtained using electron-transfer photosensitizers. q

Research paper thumbnail of Esquema Metodología

Curso de Metodología de la Investigación en las ciencias sociales Metodología (Origen, concepto y... more Curso de Metodología de la Investigación en las ciencias sociales Metodología (Origen, concepto y clasificación) Realizar un proyecto de investigación (tipo de investigación) en materia de ciencias sociales:

Research paper thumbnail of Synthesis of Activated Monomers for Cationic Photopolymerization

Journal of Macromolecular Science, Part A, 2004

A series of novel cationically photopolymerizable epoxide and vinyl ether monomers bearing substi... more A series of novel cationically photopolymerizable epoxide and vinyl ether monomers bearing substituted benzyl ether groups were prepared. Monomers with one methoxy, methylenedioxy, and three methoxy groups on the aromatic ring of the benzyl ether group were synthesized by straightforward methods. Kinetic studies using real‐time infrared spectroscopy of the cationic photopolymerizations of these novel monomers showed that those monomers with

Research paper thumbnail of Synthesis of Novel Hexathiolated Squalene and Its Thiol-Ene Photopolymerization with Unsaturated Monomers

Green and Sustainable Chemistry, 2012

In this work is described the synthesis of a multifunctional thiolated squalene. Thiol-ene coupli... more In this work is described the synthesis of a multifunctional thiolated squalene. Thiol-ene coupling reactions were employed to functionalize the six double bonds of squalene, using thiolacetic acid. Hydrolysis of the resulting thioacetates, rendered the corresponding hexathiolated squalene SQ6SH. This compound was further photopolymerized separately with triallyl cyanurate, pentaerythritol triacrylate and diethyleneglycol divinyl ether. Real Time FTIR kinetics revealed that homopolymerization of the ene monomers took place in addition to the thiol-ene photopolymerization. Flexible films were obtained when SQ6SH was photopolymerized in bulk with the above mentioned unsaturated monomers.

Research paper thumbnail of Design and synthesis of highly reactive photopolymerizable epoxy monomers

Journal of Polymer Science Part A-polymer Chemistry, 2001

The synthesis of a series of novel cationically photopolymerizable epoxide monomers bearing benzy... more The synthesis of a series of novel cationically photopolymerizable epoxide monomers bearing benzyl, allyl, and propargyl acetal and ether groups that can stabilize free radicals was carried out. These monomers display enhanced reactivity in cationic photopolymerization in the presence of certain onium salt photoinitiators. Specifically, this article describes schemes for the synthesis of cycloaliphatic epoxy monomers bearing free-radical stabilizing groups. During UV irradiation of an onium salt cationic photoinitiator, the aryl radicals that are generated abstract labile protons present in such monomers to generate the corresponding carbon-centered radicals. Subsequently, these radicals can interact with the onium salt by a redox mechanism to induce the decomposition of these salts. The overall result is that additional cationic species are generated by this mechanism that increase the rate and extent of the cationic ring-opening polymerization of the epoxide monomer. An investigation of the photopolymerizations of the monomers prepared during this work was carried out using Fourier transform real-time infrared spectroscopy, and conclusions were drawn with respect to the relationship between their structures and reactivity. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2385–2395, 2001

Research paper thumbnail of Synthesis of epoxy monomers that undergo synergistic photopolymerization by a radical-induced cationic mechanism

Journal of Polymer Science Part A-polymer Chemistry, 2001

A series of novel, cycloaliphatic, cationically photopolymerizable epoxide monomers bearing benzy... more A series of novel, cycloaliphatic, cationically photopolymerizable epoxide monomers bearing benzyl ether groups were prepared. These monomers display a considerable enhancement in the rate of their cationic ring-opening polymerizations in comparison with monomers that do not contain such groups. In this article, a synergistic free-radical mechanism is proposed that accounts for this effect, and supporting evidence is offered for its verification. During UV irradiation of an onium salt cationic photoinitiator, the aryl radicals that are generated abstract labile benzyl hydrogens present in such monomers to generate the corresponding carbon-centered radicals. Subsequently, these radicals are oxidized to benzyl carbocations by the onium salt via a nonphotochemical chain process. The observed increase in the rate and extent of the cationic ring-opening polymerization of the epoxide monomers is due to the aforementioned mechanism, which effectively increases the number of reactive cationic species present during polymerization. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3578–3592, 2001

Research paper thumbnail of Benzyl alcohols as accelerators in the photoinitiated cationic polymerization of epoxide monomers

Journal of Polymer Science Part A-polymer Chemistry, 2002

Benzyl alcohols display marked accelerating effects on the onium salt photoinitiated cationic rin... more Benzyl alcohols display marked accelerating effects on the onium salt photoinitiated cationic ring-opening polymerizations of epoxide monomers. The participation of radicals in these polymerizations was demonstrated, and a pronounced accelerating effect on the polymerization rate was observed depending on the character of the substituent on the benzene ring of the alcohol. 4-Methoxybenzyl alcohol was considerably more reactive than benzyl alcohol, whereas the analogous chloro- and nitrosubstituted compounds were less reactive. Piperonyl alcohol was even more reactive as an accelerator in these polymerizations. The UV irradiation of an onium salt cationic photoinitiator generates Brönsted acids that initiate the cationic ring-opening polymerization of the epoxide monomer. In the presence of benzyl alcohol, the usual polymerization mechanism is diverted and proceeds by a more-rapid activated monomer mechanism. As a result, benzyl ether groups are incorporated at the termini of the polymer chains. Aryl radicals that are also generated by photolysis of the onium salt abstract labile benzyl ether protons, and the benzyl ether radicals that are produced are subsequently oxidized by the onium salt to afford the corresponding benzyl carbocations. This takes place by a chain process. The polymer bound benzyl cations serve as additional sites for the initiation of cationic polymerization. It is proposed that these two mechanisms acting in synergy with one another account for the observed accelerating effect on the polymerization rate. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2298–2309, 2002

Research paper thumbnail of Synthesis of a novel biopolymer by means of Thiol-Ene Photopolymerization using diallyl sucrose and dithiotreitol as comonomers

MRS Proceedings, 2010

ABSTRACT

Research paper thumbnail of Synthesis of novel highly reactive silicone-epoxy monomers for cationic photopolymerizations

Polymer, 2005

A series of novel cationically photopolymerizable silicone-epoxide monomers bearing substituted b... more A series of novel cationically photopolymerizable silicone-epoxide monomers bearing substituted benzyl ether groups were prepared. Monomers with methoxy groups on the aromatic ring of the benzyl ether group were synthesized by sequential hydrosylation reactions of 1,1,3,3-tetramethyl disiloxane. Kinetic studies using real-time infrared spectroscopy of the cationic photopolymerizations of these novel monomers showed that those monomers with methoxy groups exhibited elevated rates of photopolymerization. The acceleration effect was explained on the basis of synergistic effects of two mechanisms, namely, the normal ring opening polymerization catalyzed by a Brönstead acid, and the cationic photopolymerization induced by the redox interaction between the free radicals formed in the backbone of the monomer and the onium salt used as photoinitiator. The methoxy groups on the aromatic ring of the benzyl ether enhance the stabilization of the carbocation formed in the structure of the monomer. Silicone-epoxy monomer with 2,5-dimethoxybenzyl ether group exhibited the higher photopolymerization rate. The latter compound can also be used as accelerator of the cationic photopolymerization of commercial silicone-epoxy monomer when used in low concentrations.

Research paper thumbnail of Development and study of a coupling agent for photocurable hybrid thiol/ene/cationic formulations

Macromolecular …, 2008

Skip to Main Content. ...

Research paper thumbnail of Interactions in the thermal and light stabilising action of novel aromatic phosphites with a 2-hydroxybenzophenone and hindered piperidine stabiliser in polyolefin …

Polymer degradation and stability, 1995

The interactions of two novel phosphite stabilisers with a commercial polymeric hindered piperidi... more The interactions of two novel phosphite stabilisers with a commercial polymeric hindered piperidine stabiliser, Chimassorb 944, and a 2-hydroxy-4-n-ctoxybenzophenone stabiliser, Cyasorb UV 531, have been examined in the thermal and photooxidation of polypropylene and high density polyethylene films using FTIR spectroscopy. The two structures are based on a bis-hindered phenolic moiety coupled to a 2-hydroxybenzophenone and a 4-amino-tetramethylpiperidine (3) chromophore.

Research paper thumbnail of Thermal and photostabilization behaviour of a novel naphthalene-HALS derivative in HDPE and PP films

Polymer degradation and …, 1999

A novel N-[-8-(2-naphthoxy)Octyl]-4-amino,2,2,6,6-tetramethylpiperidine stabiliser has been synth... more A novel N-[-8-(2-naphthoxy)Octyl]-4-amino,2,2,6,6-tetramethylpiperidine stabiliser has been synthesised and characterised and its thermal and photostabilising performance examined in both high density polyethylene and polypropylene ®lms. Its performance has been compared with that of a commercial hindered piperidine light stabiliser, Tinuvin 770 together with the eects of naphthalene. Using FTIR analysis, the naphthoxy-HALS showed excellent properties as a thermal and photostabiliser, showing strong autosynergism in the former case. Comparisons with Tinuvin 770, showed that the naphthalenic moiety of the molecule plays a role in the thermal stabilization process by scavenging oxygen. Naphthalene itself exhibited some degree of thermal stabilization and reversed its behaviour from being a weak stabilizer at low concentrations to a prooxidant at higher concentrations. The same pattern of stabilization was observed during the photoaging of polypropylene with the exception of the mixture of Tinuvin 770 and naphthalene which was found to exhibit the best performance at the higher concentration. #

Research paper thumbnail of Preparation of a crosslinked sucrose polymer by thiol–ene photopolymerization using dithiothreitol as comonomer

Carbohydrate Polymers, 2010

The thiol-ene photopolymerization technique was used to prepare a crosslinked sucrose polymer. Su... more The thiol-ene photopolymerization technique was used to prepare a crosslinked sucrose polymer. Sucrose was chemically modified to introduce two allyl groups, however, in the synthesis were also produced mono and triallyl derivatives. After purification by column chromatography, a fraction (F2A2S) with 94% diallyl sucrose (A2S), 4% of triallyl sucrose (A3S) and 2% of monoallyl sucrose (A1S) was obtained. This fraction was subsequently photopolymerized with dithiothreitol (DTT) which is a difunctional thiol. The presence of small concentration of A3S in F2A2S helped to crosslink in situ the obtained polythioether. Photopolymerization kinetics were determined using the Real-Time Infrared technique. It was found that photopolymerization can proceed in the absence of photoinitiators but the rate of photopolymerization and conversion increased considerably when different photoinitiators at 1 mol% were used and when the intensity of UV light was increased. The analysis by DMA of probes of the obtained sucrose polythioether revealed that the difunctionality of both comonomers, A2S and DTT, resulted in flexible materials with a T g of 30 • C and high storage modulus values. The sucrose polythioether was completely degraded in 2 h in strongly acidic medium. Additionally, the ability of water to absorb the prepared material was tested. We found that it was pH dependent with the maximum absorption at pH = 14. The biopolymer displayed high thermal stability up to 230 • C.

Research paper thumbnail of Effect of introducing a cationic system into a thiol‐ene photopolymerizable formulation

Journal of Polymer …, 2007

Hybrid materials derived from a thiol-ene and cationic polymerization were obtained from concomit... more Hybrid materials derived from a thiol-ene and cationic polymerization were obtained from concomitant polymerization. The hybrid materials were cured by both photopolymerization and thermally induced polymerization. The kinetics of the photopolymerization were measured using time resolved-IR and optical pyrometry. The nucleophilic character of the polysulfide obtained initially in the thiol-ene polymerization inhibited the development of the cationic photoinitiated polymerization of epoxy monomers. Besides, the epoxide groups underwent a proton catalyzed addition reaction with the thiols to form new sulfides groups in the reaction mixture. It is proposed that the formed sulfides can terminate the growing polyether chains forming dormant species like trialkylsulfonium salts. These salts promote the thermal polymerization of the epoxy monomer in a post treatment, producing hard and transparent materials. V V C 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4829-4843, 2007

Research paper thumbnail of Development of Hybrid Polymeric Materials Based on Thiol‐Ene/Cationic Formulations

Macromolecular …, 2008

Novel materials were prepared from dual photo and thermal polymerization of hybrid thiolene/catio... more Novel materials were prepared from dual photo and thermal polymerization of hybrid thiolene/cationic systems. In the first stage, the thiol-ene system proceeded to high conversions, while the cationic photopolymerization was inhibited. The formation of sulfides during this stage was the main factor for the inhibition of the cationic photopolymerization of the epoxy monomers. Once those sulfides were formed, they reacted with the oxonium-terminated growing polyether chains to form trialkylsulfonium salts. These salts promoted the thermal polymerization of the epoxy monomers in the second stage. The viscoelastic properties of the resulting polymers were measured by DMA.

Research paper thumbnail of Thermal and photo-oxidative stabilisation of polyolefin films: mode of action of novel naphthalene-hindered piperidine derivatives

Polymer degradation and stability, 1998

Research paper thumbnail of An effective method to prepare sucrose polymers by Thiol-Ene photopolymerization

Carbohydrate …, 2009

... a , E-mail The Corresponding Author , Aida E. Garcia Valdéz a , Marty Georgina Martinez Aguil... more ... a , E-mail The Corresponding Author , Aida E. Garcia Valdéz a , Marty Georgina Martinez Aguilar a and Maria Lydia Berlanga Duarte ... to prepare materials with potential applications as restorative dental resins (Carioscia, 2005; Lu, Carioscia, Stansbury, and Bowman, 2005) and ...

Research paper thumbnail of A kinetic study of the acceleration effect of substituted benzyl alcohols on the cationic photopolymerization rate of epoxidized natural oils

Polymer, 2005

The rate of the cationic photopolymerization of epoxidized natural oils was enhanced by the addit... more The rate of the cationic photopolymerization of epoxidized natural oils was enhanced by the addition of several mono, di and trisubstituted benzyl alcohols. The epoxidation of vegetable oils was achieved by using 30% hydrogen peroxide with methyl trioxo rhenium (MTO) as a phase transfer catalyst. Then, the effect of different methoxy-substituted benzyl alcohols on the curing rate was evaluated, using the real-time FT-IR technique. The overall result was an increase in the curing rate. The acceleration effect was explained on the basis of synergistic effects of two mechanisms, namely, the radical induced cationic photopolymerization and the activated monomer mechanism. Epoxidized oils with 2,5-dimethoxybenzyl alcohol as an accelerator exhibited the highest photopolymerization rate. Higher conversions were obtained using electron-transfer photosensitizers. q

Research paper thumbnail of Esquema Metodología

Curso de Metodología de la Investigación en las ciencias sociales Metodología (Origen, concepto y... more Curso de Metodología de la Investigación en las ciencias sociales Metodología (Origen, concepto y clasificación) Realizar un proyecto de investigación (tipo de investigación) en materia de ciencias sociales: