| 1. |
- Gazzotti, Stefano, et al.
(author)
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Cellulose nanofibrils as reinforcing agents for PLA-based nanocomposites : An in situ approach
- 2019
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In: Composites Science And Technology. - : Elsevier BV. - 0266-3538 .- 1879-1050. ; 171, s. 94-102
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Journal article (peer-reviewed)abstract
- One-pot in situ polymerization approach was explored for the preparation of polylactide (PLA)-cellulose nano-fibril (CNF) bio-nanocomposites. CNF were first prepared through enzymatic and mechanical treatment of bleached hardwood kraft pulp. The bio-nanocomposites- were then fabricated through ring opening polymerization (ROP) of L-lactide, in the presence of various amounts of fibrils. Molecular weight, thermal properties, surface morphology, mechanical and wettability properties of the PLA-CNF nanocomposites were evaluated. DSC analysis demonstrated the effect of CNF on crystallization and crystalline morphology of PLA. Improved modulus for the nanocomposites with respect to standard PLA was demonstrated, however, the differences in tensile stress were small probably due to the counteracting effects of reinforcement from CNF and the decreasing molecular weight as a function of CNF concentration. The absence of pulled-out fibers was assessed, highlighting the strong interface and covalent attachment of PLA chains on CNF surface. Finally, the covalent bonding of PLA chains on CNF surface was demonstrated by isolating the non-soluble part, consisting of PLA-grafted CNF, and characterization of this residue.
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| 2. |
- Gazzotti, Stefano, et al.
(author)
-
DOX mediated synthesis of PLA-co-PS graft copolymers with matrix-driven self-assembly in PLA-based blends
- 2022
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In: European Polymer Journal. - : Elsevier BV. - 0014-3057 .- 1873-1945. ; 170, s. 111157-
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Journal article (peer-reviewed)abstract
- Intriguing phase morphology was formed through self-assembly of polylactide-polystyrene (PLA-co-PS) graft copolymers blended with polylactide (PLA). PLA-co-PS graft copolymers were synthesized by exploiting a styrene-functionalized 1,3-Dioxolan-4-one (StyDOX) monomer through a two-step procedure and their structure was confirmed. Different amounts of PLA-co-PS and commercial PLA were solution cast to blend films. Etching of amorphous PLA revealed the presence of spherical micrometer sized domains dispersed within the films, arising from the self-assembly behavior of PLA-co-PS caused by the immiscibility of PS-grafts in the PLA matrix. EDS and IR imaging analyses further revealed that these microspheres were characterized by a PS-rich core opposed to the PLA-rich outer shell, which is expected to be miscible and able to form favorable interactions with the PLA matrix. PLA/PS blends were also prepared with different loadings of PLA-co-PS. The ability of PLA-co-PS to compatibilize the two phases was assessed through rheological analyses. Finally, the possibility to chemically recycle the copolymer was evaluated.
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| 3. |
- Gazzotti, Stefano, et al.
(author)
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One-Pot Synthesis of Sustainable High-Performance Thermoset by Exploiting Eugenol Functionalized 1,3-Dioxolan-4-one
- 2018
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In: ACS Sustainable Chemistry and Engineering. - : American Chemical Society (ACS). - 2168-0485. ; 6:11, s. 15201-15211
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Journal article (peer-reviewed)abstract
- 1,3-Dioxolan-4-one (DOX) chemistry was explored for production of "one-pot" biobased polyester thermosets. DOX monomer was first functionalized by naturally occurring eugenol to introduce a structural element, which could induce cross-linking reaction through cationic polymerization of the double bond. The feasibility of polymerizing DOX monomers bearing bulky side groups was proven by model phenol-substituted DOX monomer (PhDOX). Once the reaction was shown to be effective, the same protocol was applied to eugenol-substituted monomer (EuDOX). A brief screening of the optimal catalyst concentration was performed, to obtain a highly cross-linked product. The synthesized thermoset showed good thermal resistance and high mechanical strength probably due to the rich aromatic content. The obtained thermoset was further subjected to microwave-assisted hydrothermal degradation test, which demonstrated complete recyclability to water or methanol soluble products. NMR and matrix-assisted laser desorption/ionization-mass spectroscopy analyses of the obtained degradation products unveiled the structure of the thermoset, strongly indicating that the polymerization of eugenol-functionalized DOX monomer resulted in polylactide-like chains connected with aromatic aliphatic segments resulting from the reaction of the eugenol double bonds. The presence of free hydroxyl and carboxyl groups sheds light on the mechanism behind the observed shape-memory and self-healing properties.
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| 4. |
- Gazzotti, Stefano, et al.
(author)
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Poly(alditol sebacate)-PLA copolymers : enhanced degradability and tunable surface properties
- 2024
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In: Polymer Chemistry. - : Royal Society of Chemistry (RSC). - 1759-9954 .- 1759-9962.
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Journal article (peer-reviewed)abstract
- The synthesis of aliphatic, degradable polyesters based on biobased alditols was investigated. Mannitol and dulcitol were employed as biobased building blocks for the synthesis of aliphatic polyesters in combination with sebacoyl chloride. In order to achieve optimal control over the macromolecular architecture of the polymer, multifunctional monomers were converted to bifunctional species through a straightforward protection strategy. Bifunctional di-O-isopropylidene derivatives were synthesized starting from mannitol and dulcitol in a one-step procedure and exploited as monomers to yield linear poly(mannitol sebacate) (PMS) and poly(dulcitol sebacate) (PDS) derivatives. The use of a bifunctional monomer allowed an optimal control over the macromolecular architecture and the synthesis of PMS and PDS-based polyols. These polyols were then employed as initiators for the synthesis of PLA-based copolymers. Two different concentrations of PMS and PDS were tested and the related effects investigated, regarding the molecular weight and thermal properties of the resulting PLA-based copolymers. Deprotection of the isopropylidene moieties on the polyol backbone was then evaluated in order to determine the influence of liberation of free OH- groups on the wettability of the materials. Finally, degradation tests were performed in different aqueous environments, showing the influence of PMS and PDS on the degradation rate of PLA-based materials. The synthesis of aliphatic, degradable polyesters based on biobased alditols was investigated.
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