Synthesis of Poly(thioether-ester) nanoparticles derived from renewable resources via thiol-ene polymerization in miniemulsion

Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro Tecnológico, Programa de Pós-Graduação em Engenharia Química, Florianópolis, 2015.Abstract : Green chemistry has drawn attention from researchers and even some industries due to concerns about the depletion of fossil oil reserves and aggravation in the global warming and other environmental issues. Polymeric materials from biofeedstocks-derived monomers are a promising environmentally friendly alternative to petrol-derived polymers, especially for high value added applications. In this context, vegetable oils and saccharides are interesting raw materials that can be applied as chemical platforms in the synthesis of novel fully renewable monomers through chemical modification. In addition, thiol-ene polymerization has been shown as a versatile tool to produce polymers from fully renewable a,?-diene monomers bearing, for example ester, ether, or amide functional groups in the backbone chain. However, works portraying the polymerization of renewable monomers through thiol-ene polymerization in dispersed medium are still uncommon. Herein, it is presented the synthesis and characterisation of poly(thioether-ester) nanoparticles via thiol-ene polymerization in miniemulsion using a monomer derived from renewable resources. The synthesis of a renewable a,?-diene diester monomer, dianhydro-D-glucityl diundec-10-enoate (DGU), produced from 10-undecenoic acid (derived from castor oil) and isosorbide (derived from starch) was performed. DGU was copolymerized with 1,4-butanedithiol (Bu(SH)2) through thiol-ene polymerization both in bulk and miniemulsion to yield linear semi-crystalline poly(thioether-ester)s. Different parameters were evaluated such as reaction temperature, initiator concentration, surfactant type and surfactant concentration. Particle size distribution and morphology was observed by DLS and TEM respectively resulting in spherical particles with an intensity average particle diameter around 200 nm. Polymer with higher molecular weight was obtained by miniemulsion polymerization when compared to bulk polymerization. Number average molecular weight of 11 kDa was obtained through miniemulsion polymerization at 80°C for 4h using AIBN at 1 mol% (in relation to Bu(SH)2). Furthermore, DSC and XRD analyses have shown that the synthesized polymer was semi-crystalline with a degree of crystallinity above 20% and Tm around 60°C. Finally, depending on the co-stabilizer type, hexadecane or Crodamol, and amount, phase segregation within polymer particles was observed through DSC.A química verde tem chamado a atenção de pesquisadores e até mesmo de algumas indústrias devido à preocupação com o esgotamento das reservas fósseis e o agravamento de problemas ambientais. Materiais poliméricos obtidos de monômeros derivados de fontes renováveis são uma alternativa ambientalmente correta aos polímeros derivados do petróleo, especialmente para aplicações de alto valor agregado. Neste contexto, óleos vegetais e sacarídeos são matérias-primas interessantes que podem ser utilizadas como plataformas químicas para a síntese de novos monômeros, completamente renováveis, através da modificação química. Além disso, polimerização tiol-eno mostrou-se uma versátil ferramenta para a produção de polímeros a partir de monômeros verdes (a,?-dienos) providos de grupos funcionais como éster, éter ou amida na cadeia principal. Entretanto, trabalhos sobre a polimerização de monômeros renováveis através da polimerização tiol-eno em meios dispersos ainda são escassos. Neste trabalho, a síntese e a caracterização de nanopartículas de poli(tioéter-éster) via polimerização tiol-eno em miniemulsão usando um monômero proveniente de fontes renováveis são apresentadas. O monômero verde utilizado é um a,?-dieno diéster, diundec-10-enoato de dianidro-D-glucitila (DGU), produzido a partir de ácido 10-undecenóico (derivado do óleo de mamona) e isosorbídeo (derivado do amido). DGU foi copolimerizado com 1,4-butanoditiol (Bu(SH)2) através polimerização tiol-eno em massa e em miniemulsão para produzir poli(tioéter-éster) linear e semicristalino. Diferentes parâmetros foram avaliados, como por exemplo temperatura, concentração de iniciador, tipo e concentração do surfactante. A distribuição de tamanho e a morfologia das partículas foram observadas por DLS e TEM respectivamente, revelando partículas esféricas com diâmetro de 200 nm. O polímero obtido pela polimerização em miniemulsão, 11 kDa onde as condições reacionais foram 80°C por 4h usando 1 mol% de AIBN (em relação ao Bu(SH)2), mostrou-se com maior massa molar em comparação àquele obtido em polimerização em massa. Análises de DSC e DRX mostraram que o polímero sintetizado é semicristalino com grau de cristalinidade de pelo menos 20% e Tm em torno de 60°C. Dependendo do tipo de co-estabilizador utilizado, hexadecano ou Crodamol, e da quantidade, pode-se observar por DSC segregação de fases nas partículas poliméricas

Improving the Performance of Photoactive Terpene-Based Resin Formulations for Light-Based Additive Manufacturing

Photocurable liquid formulations have been a key research focus for the preparation of mechanically robust and thermally stable networks. However, the development of renewable resins to replace petroleum-based commodities presents a great challenge in the field. From this perspective, we disclose the design of photoactive resins based on terpenes and itaconic acid, both potentially naturally sourced, to prepare photosets with adjustable thermomechanical properties. Biobased perillyl itaconate (PerIt) was synthesized from renewable perillyl alcohol and itaconic anhydride via a scalable solvent-free method. Photoirradiation of PerIt in the presence of a multiarm thiol and photoinitiator led to the formation of networks over a range of compositions. Addition of nonmodified terpenes (perillyl alcohol, linalool, or limonene) as reactive diluents allowed for more facile preparation of photocured networks. Photosets within a wide range of properties were accessed, and these could be adjusted by varying diluent type and thiol stoichiometry. The resins showed rapid photocuring kinetics and the ability to form either brittle or elastic materials, with Young’s modulus and strain at break ranging from 3.6 to 358 MPa and 15 to 367%, respectively, depending on the chemical composition of the resin. Glass transition temperatures (Tg) were influenced by thioether content, with temperatures ranging from 5 to 43 °C, and all photosets displayed good thermal resistance with Td,5% > 190 °C. Selected formulations containing PerIt and limonene demonstrated suitability for additive manufacturing technologies and high-resolution objects were printed via digital light processing (DLP). Overall, this work presents a simple and straightforward route to prepare renewable resins for rapid prototyping applications

Syntheses of biobased nanocarriers via click chemistry in miniemulsion for drug delivery in agriculture

Tese (doutorado) - Universidade Federal de Santa Catarina, Centro Tecnológico, Programa de Pós-Graduação em Engenharia Química, Florianópolis, 2019.Abstract: The sustained release of agrochemicals in agriculture is a promising solution to reduce eco-toxicological and increase the effectiveness of agrochemicals administration. Although agrochemicals are necessary to the agricultural scenario, due to, e.g., voluminous production, devastating fungal diseases and soil depletion, the indiscriminate use of fertilizers and pesticides has contributed to the development of harmful impacts in the environment, pest resistance and human health. Biopolymer nanocarriers are environmentally friendly alternatives due to their renewable origin and biodegradability, which enable their integration into biogeochemical cycles. Lignin and cellulose are worldwide available biopolymers produced as waste in millions of tonnes every year and therefore are interesting inexpensive renewable raw materials suitable, after chemical modification, for macromolecular nanostructures syntheses. Kraft lignin was esterified with methacrylic anhydride with > 90 % of functionalisation to yield lignin methacrylate. Lignin nanocarriers (NCs) were produced by aza-Michael click addition in miniemulsion and several fungicides ? namely azoxystrobin, pyraclostrobin, tebuconazole, and boscalid ? were encapsulated in situ, thereby demonstrating the wide-ranging applicability of the method. NCs with average particle size of 200 ? 300 nm were obtained, with 70 to 99% encapsulation efficiencies. The crosslinking, using the biobased amines spermine and spermidine as crosslinking agents, was monitored by the decrease in the band at 950 cm-1 in the infrared spectra. Native cellulose, 45 % of crystallinity, was submitted to transesterification of cellulose to produce colza oil cellulose esters and to esterification to produce undec-10-enoic cellulose esters (UACEs), for such, two different systems were used, DBU/CO2 switchable solvent, a novel environmentally friendly approach for cellulose solubilisation, and DMAc/LiCl, the classical method. The obtained degrees of substitution were up to 2.4, and chemical modification has entailed some changes in molecular weight, thermal properties and crystallinity to cellulose esters. Cellulose nanocarriers were synthesized from UACEs by thiolene addition in miniemulsion and the crosslinking was qualitatively monitored by the double bond consumption observed at 907 cm-1 in infrared spectra. NCs in the size range of 150 ? 250 nm were obtained. Captan and pyraclostrobin were encapsulated in high efficiency, > 70 %, measured by HPLC. Overall, NCs formulations presented lower minimum inhibitory concentrations than their bulk counterparts against phytopathogenic fungi. Lignin NCs successfully inhibited the growth up to ca. 90 % of Phaeomoniella chlamydospora and Phaeoacremonium minimum, fungi associated to the worldwide occurring fungal grapevine trunk disease Esca. In addition, cellulose NCs have successfully inhibited spore germination and mycelial growth P. minimum and Neonectria ditissima up to 80 % of inhibition depending on the formulation and the fungus strain tested. Trunk diseases cannot be controlled by aspersion of fungicides on the crop and cause the dieback and death of plants, as well as decrease crop yields impacting on commercial trades. Novel strategies to fight these diseases on-field are still under development and biobased polymer nanocarriers loaded with fungicides are a promising approach to overcome destructive trunk diseases that affect crops globally by, for instance, trunk injection, which could keep the plant under protection over years by slow sustained release mediated by the presence of fung