Synthesis and structure-property relationships of 3-methylene-2-pyrrolidone-based (co)polymers

Heyns, Ingrid Marie (2015-03)

Thesis (MSc)--Stellenbosch University, 2015.

Thesis

ENGLISH ABSTRACT: Recently, the incorporation of renewable resources as a substitute to fossil fuels in the synthesis of polymers/materials has attracted a vast amount of interest, particularly for the green advantages offered. This study describes the synthesis, polymerization and characterization of 3-methylene-2-pyrrolidone-based (3M2P) monomers, with 3M2P being a naturally occurring lactam moiety. Two different chemical syntheses of the monomer, 3M2P, were attempted, with the first approach involving the Wittig reaction for the formation of the exo-cyclic methylene group. The second approach involved the dehydration of 3-(hydroxymethyl)-2-pyrrolidone. Preference was given to the Wittig approach during the study conducted, as the dehydration reaction of the second approach was unsuccessful. The purification and control over by- and side-products of the Wittig approach were optimized and confirmed by various spectroscopic techniques. Statistical copolymerizations of 3M2P-based monomers revealed the formation of oligomers, while in situ 1H NMR spectroscopic experiments failed to quantify the incorporation or consumption of either monomers due to a peak overlap. Conventional radical homopolymerizations of 3M2P were successful and polymers were characterized by NMR spectroscopy and size exclusion chromatography (SEC). It was discovered that the polymer, P(3M2P), has very good thermal stability with a Tg = 285 °C and a decomposition temperature between 400-500 °C. P(3M2P) proved to be extremely water-soluble, but it did not dissolve in most organic solvents. The thermal and solubility behaviour were ascribed to the structurally rigid lactam moiety and its strong hydrogen-bonding ability. Cytotoxicity testing revealed that P(3M2P) was completely non-toxic. Finally, the polymerization versatility of 3M2P was evaluated via different living radical polymerization techniques in an attempt to create well-defined macromolecules with precision. SET-LRP and RAFT polymerizations proved to be controlled, with a Ð < 1.5, whilst NMP exhibited poor control. The RAFT polymerization was extended to an amphiphilic block copolymer with the first segment being polystyrene and the second segment, P(3M2P). During the chain-extension only oligomeric 3M2P species were incorporated.

AFRIKAANSE OPSOMMING: Met die toenemende belangstelling in die gebruik van meer omgewingsvriendelike materiale en die soeke na plaasvervangers vir nie-hernieubare fossielbrandstowwe vir die sintese van polimere, is daar ‘n alewige toename in die ontwikellinge van prosesse om die bogenoemde te bevorder. ‘n Benadering om die probleem te oorkom is om van hernubare hulpbronne gebruik te maak. Gevolglik fokus hierdie studie op die sintese, polimerisasie en ‘n ontleding van die karaktereienskappe van 3-metileen-2-pyrolidoon (3M2P) monomere. 3M2P is ‘n laktaam gedeelte wat natuurlik voorkom. Met die sintese van 3M2P, is twee verskillende chemiese benaderings aangepak. Voorkeur is gegee aan die benadering wat van die Wittig reaksie gebruik maak vir die vorming van die ekso-sikliese metileen groep, aangesien die tweede benadering, wat die dehidrasie van 3-(hydroksiemetiel)-2-pyrolidoon behels het, nie die dehidrasie van dié spesifieke reaksie teweeg kon bring nie. Die suiwering en beheer oor beide mede- en neweprodukte is geoptimaliseer, aangepas vir grootskaalse produksie en is bevestig deur verskeie spektroskopiese tegnieke. Statistiese kopolimerisasies van die 3M2P-gebaseerde monomere, het die vorming van oligomere onthul, terwyl in situ 1H KMR spektroskopie experimente versuim het om die gebruik en verbruik van enige van die monomere te definieer, a.g.v. die oorvleuling van pieke. Daarteenoor, was die meer algemene radikale homopolimerisasies van 3M2P meer suksesvol en dit was moontlik om die polimere se karaktereienskappe te definieer deur beide KMR spektroskopie and SEC. Daar is bevind dat die polimeer, P(3M2P), ‘n baie bevredigende termiese stabiliteit met Tg = 285 °C en ‘n ontbindingstemperatuur van tussen 400-500 °C, gehandhaaf het. Daar is verder bevind dat P(3M2P) water-oplosbaar was en weerstand tot die meeste organiese oplosmiddels gebied het. Die termiese en oplosbaarheidseienskappe is toeskryfbaar aan die strukturele-rigied laktaam en die sterk potensiaal om waterstofbindings te vorm. Sitotoksiese toetse het ook onthul dat P(3M2P) geheel en al nie-toksies is. Laastens is die vermoë van 3M2P om polimere te vorm, geevalueer deur die gebruik van verskeie lewende radikaal polymerisasie tegnieke in pogings om wel-gedefinieerde makromolekules met presisie te ontwikkel. SET-LRP en RAFT polimerisasies het gedui daarop dat beheer oor die reaksie behou is, met ‘n Ð < 1.5, terwyl NMP op die verlies in beheer gedui het. Die RAFT polimerisasies is verder uitgebrei tot ‘n amfifiliese blokkopolimeer, waarvan die eerste segment polistireën en die tweede segment P(3M2P), ingesluit het. Met die ketting-verlenging daarvan, is daar slegs oligomeriese 3M2P spesies geïnkorporeer.

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