This thesis addresses two macro themes concerning the sustainable development which implies reduction of petroleum dependence and minimization of carbon footprint. The Part I “Innovative additives as viscosity modifiers for energy saving lubricants” concerns the design and development of new viscosity modifier additives (VMs), which are fundamental to regulate the viscosity/temperature dependence in lubricant oils enabling them to prevent energy loss due to friction phenomena which determines an increment in fuel consumption and consequently the associated emission. New controlled star and comb polymer architectures with styrene-b-isoprene copolymer arms were synthesized. Arms with very low molecular weight dispersion were obtained by anionic polymerization. Star like structures were produced by arm-first method and new comb-copolymers were achieved through “grafting onto” method. Four- and six-arm star polymer structures were prepared by adding chloro alkylsilane cores to living polymeric arms. Comb polymers were synthesized by adding a new polymeric skeleton made of poly(t-butyl-6-5-norbornene-exo-2,3-dicarboxyimidohexanoate) as terminal agent during the arm polymerization. Comb copolymers with up 16-arms were obtained. The isoprene units of styrene-diene copolymers were hydrogenated to make their structure stable to oxidative and mechanical stress. After hydrogenation, the six-arm star copolymers exhibited a good low temperature behaviour, showing excellent compatibility with the pour point depressant and mechanical shear stability slightly better than most commercial VMs. Moreover, it is expected that after hydrogenation the new comb copolymers will have thickening efficiency superior to that of the hydrogenated star copolymers for their large number of arms. The Part II “Sulfur-rich polymers” regards the reuse of carbon disulfide (CS2) (Part II A) and elemental sulfur (Part II B), as feedstocks for polymer production, to help to overcome “excess sulfur problem” and to produce high value products without depleting natural resources. In part II A, for the first time an investigation of the copolymerization of CS2 and cyclohexene sulfide (CHS) catalysed by salen and salphen chromium complexes and PPNX salt as cocatalyst was performed at different times and temperatures. Both catalytic systems produce both polymer and cyclic products. Salphen based catalysts, in comparison with salen based ones, show higher productivity and selectivity for polymers with high molecular weight up to 18 kg/mol when the reaction is carried out at 25 °C. At higher temperature with (salphen)CrCl, the maximum value of selectivity for copolymers (72 %) was obtained at short reaction time (3 h). It was found that poly(trithiocyclohexylcarbonate)s possess high refractive index (n > 1.72), and antimicrobial proprieties against E. Coli and S. Aureus which along with the Tg values of 80 °C make these materials suitable for interesting applications different from those of poly(trithiopropylencarbonate)s. In part II B, dipentene, a bio-based sustainable feedstock, was used for first time in combination with elemental sulfur, to produce green-polysulfides alternative to those produced from enantiomeric limonene. Poly(S-dipentene)s with high sulfur content (> 50 %) were synthesized by catalytic inverse polymerization in presence of zinc-based accelerators at 140 °C. Accelerators allowed to reduce mixing time between dipentene and sulfur. Stable ter-polysulfides with depressed depolymerization reactions were achieved, by adding 10 % of natural crosslinker such as garlic oil, myrcene and diallyl disulfide. Ter-polysulfides produced are soft solids with Tg values between -1 and 4 °C. Shape persistent blend of ter-polysulfide and commercial polystyrene was prepared. The polysulfide-polystyrene blend resulted processable, mouldable and able to remove ferric ions from aqueous solution.

Questa tesi ha affrontato due macro-temi riguardanti lo sviluppo sostenibile. La parte I “Additivi innovativi come modificatori di viscosità per lubrificanti a risparmio energetico" ha riguardato la progettazione e lo sviluppo di nuovi additivi modificatori di viscosità (VM). Essi sono fondamentali per regolare la dipendenza viscosità/temperatura negli oli lubrificanti consentendo loro di prevenire perdite di energia dovute all’attrito che determinano un incremento del consumo di carburante e delle relative emissioni. Sono state sintetizzate delle nuove strutture polimeriche ben definite a stella e a pettine con braccia di copolimeri stirene-b-isoprene. Braccia con bassa polidispersità sono state sintetizzate da polimerizzazione anionica, le strutture a stella sono state prodotte con il metodo arm-first e le strutture a pettine mediante il metodo grafting onto. I polimeri stellari a 4 e 6 braccia sono stati preparati aggiungendo dei nuclei di cloro alchilsilano alle braccia polimeriche viventi. I polimeri a pettine sono stati sintetizzati aggiungendo un nuovo scheletro polimerico fatto di poli(t-butil-6-5-norbornene-eso-2,3-dicarbossiimidoesanoato) come terminatore delle braccia polimeriche viventi. Sono stati ottenuti copolimeri a pettine aventi fino a 16 braccia. Le unità di isoprene sono state idrogenate per renderli stabili alle sollecitazioni ossidative e meccaniche. Dopo l'idrogenazione, i copolimeri stellari a 6 braccia hanno mostrato un buon comportamento a bassa temperatura e un'eccellente compatibilità con il pour point depressant e una stabilità al taglio migliore della maggior parte delle VM commerciali. Inoltre, si prevede che dopo l'idrogenazione i nuovi copolimeri a pettine avranno un'efficienza di ispessimento superiore a quella dei copolimeri stellari idrogenati per il loro gran numero di braccia. La Parte II " Polimeri ricchi di zolfo" ha previsto il riutilizzo del disolfuro di carbonio (CS2) (Parte II A) e dello zolfo elementare (Parte II B), come materia prima per la produzione di polimeri, al fine di aiutare a superare "il problema dello zolfo in eccesso" e produrre materiali di alto valore. Nella parte II A, per la prima volta è stata studiata la copolimerizzazione tra CS2 e cicloesene solfuro con catalizzatori di cromo tipo salen e salphen e sali di PPNX a 25 e 50 °C. Entrambi i sistemi catalitici hanno prodotto sia materiale polimerico che ciclico. I catalizzatori di tipo salphen, rispetto a quelli di tipo salen, hanno mostrato una maggiore produttività e selettività per il polimero. Sono stati ottenuti politritiocarbonati ad alto peso molecolare fino a 18 kg/mol. A 50°C con (salphen)CrCl, il valore massimo di selettività per i copolimeri è stato ottenuto a 3 h. I poli(tritiocicloesene carbonati) hanno alto indice di rifrazione (n > 1.72) e proprietà antimicrobiche che con i valori di Tg di 80 °C rendono questi materiali adatti per applicazioni interessanti diverse da quelle dei poli(tritiopropilenecarbonati). Nella parte II B, il dipentene, una miscela di monoterpeni sostenibile e rinnovabile, è stato usato per la prima volta in combinazione con zolfo elementare, per produrre polisolfuri green ed economici alternativi a quelli prodotti dal limonene. Poli(S-dipenteni) con alto contenuto di zolfo (> 50 %) sono stati sintetizzati mediante polimerizzazione inversa catalitica in presenza di acceleratori a base di zinco. Gli acceleratori hanno permesso di ridurre il tempo di miscelazione tra dipentene e zolfo. Sono stati ottenuti ter-polisolfuri stabili, aggiungendo il 10 % di un crosslinker naturale come garlic oil, mircene e disolfuro di diallile. I ter-polisolfuri prodotti sono solidi morbidi con valori di Tg tra -1 e 4 °C. Sono state preparate delle miscele di ter-polisolfuro e polistirene che mantengono la forma, processabili e in grado di rimuovere gli ioni ferrici da soluzione acquosa.

(2022). Polymers for a green and sustainable economy: star and comb polymers as viscosity modifiers and high sulfurated polymers. (Tesi di dottorato, Università degli Studi di Milano-Bicocca, 2022).

Polymers for a green and sustainable economy: star and comb polymers as viscosity modifiers and high sulfurated polymers

SILVANO, SELENA
2022

Abstract

This thesis addresses two macro themes concerning the sustainable development which implies reduction of petroleum dependence and minimization of carbon footprint. The Part I “Innovative additives as viscosity modifiers for energy saving lubricants” concerns the design and development of new viscosity modifier additives (VMs), which are fundamental to regulate the viscosity/temperature dependence in lubricant oils enabling them to prevent energy loss due to friction phenomena which determines an increment in fuel consumption and consequently the associated emission. New controlled star and comb polymer architectures with styrene-b-isoprene copolymer arms were synthesized. Arms with very low molecular weight dispersion were obtained by anionic polymerization. Star like structures were produced by arm-first method and new comb-copolymers were achieved through “grafting onto” method. Four- and six-arm star polymer structures were prepared by adding chloro alkylsilane cores to living polymeric arms. Comb polymers were synthesized by adding a new polymeric skeleton made of poly(t-butyl-6-5-norbornene-exo-2,3-dicarboxyimidohexanoate) as terminal agent during the arm polymerization. Comb copolymers with up 16-arms were obtained. The isoprene units of styrene-diene copolymers were hydrogenated to make their structure stable to oxidative and mechanical stress. After hydrogenation, the six-arm star copolymers exhibited a good low temperature behaviour, showing excellent compatibility with the pour point depressant and mechanical shear stability slightly better than most commercial VMs. Moreover, it is expected that after hydrogenation the new comb copolymers will have thickening efficiency superior to that of the hydrogenated star copolymers for their large number of arms. The Part II “Sulfur-rich polymers” regards the reuse of carbon disulfide (CS2) (Part II A) and elemental sulfur (Part II B), as feedstocks for polymer production, to help to overcome “excess sulfur problem” and to produce high value products without depleting natural resources. In part II A, for the first time an investigation of the copolymerization of CS2 and cyclohexene sulfide (CHS) catalysed by salen and salphen chromium complexes and PPNX salt as cocatalyst was performed at different times and temperatures. Both catalytic systems produce both polymer and cyclic products. Salphen based catalysts, in comparison with salen based ones, show higher productivity and selectivity for polymers with high molecular weight up to 18 kg/mol when the reaction is carried out at 25 °C. At higher temperature with (salphen)CrCl, the maximum value of selectivity for copolymers (72 %) was obtained at short reaction time (3 h). It was found that poly(trithiocyclohexylcarbonate)s possess high refractive index (n > 1.72), and antimicrobial proprieties against E. Coli and S. Aureus which along with the Tg values of 80 °C make these materials suitable for interesting applications different from those of poly(trithiopropylencarbonate)s. In part II B, dipentene, a bio-based sustainable feedstock, was used for first time in combination with elemental sulfur, to produce green-polysulfides alternative to those produced from enantiomeric limonene. Poly(S-dipentene)s with high sulfur content (> 50 %) were synthesized by catalytic inverse polymerization in presence of zinc-based accelerators at 140 °C. Accelerators allowed to reduce mixing time between dipentene and sulfur. Stable ter-polysulfides with depressed depolymerization reactions were achieved, by adding 10 % of natural crosslinker such as garlic oil, myrcene and diallyl disulfide. Ter-polysulfides produced are soft solids with Tg values between -1 and 4 °C. Shape persistent blend of ter-polysulfide and commercial polystyrene was prepared. The polysulfide-polystyrene blend resulted processable, mouldable and able to remove ferric ions from aqueous solution.
COMOTTI, ANGIOLINA
TRITTO, INCORONATA
BOGGIONI, LAURA
polimero star; polimero comb; viscosità; polisolfuri; dipentene
star polymer; comb polymer; viscosity; polysulfide; dipentene
CHIM/05 - SCIENZA E TECNOLOGIA DEI MATERIALI POLIMERICI
English
25-mag-2022
SCIENZA E NANOTECNOLOGIA DEI MATERIALI
34
2020/2021
embargoed_20250525
(2022). Polymers for a green and sustainable economy: star and comb polymers as viscosity modifiers and high sulfurated polymers. (Tesi di dottorato, Università degli Studi di Milano-Bicocca, 2022).
File in questo prodotto:
File Dimensione Formato  
phd_unimib_846273.pdf

embargo fino al 25/05/2025

Descrizione: Polymers for a green and sustainable economy: star and comb polymers as viscosity modifiers and high sulfurated polymers
Tipologia di allegato: Doctoral thesis
Dimensione 6.04 MB
Formato Adobe PDF
6.04 MB Adobe PDF   Visualizza/Apri   Richiedi una copia

I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.

Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/10281/378874
Citazioni
  • Scopus ND
  • ???jsp.display-item.citation.isi??? ND
Social impact