Increasing concerns regarding the depletion of fossil-based resources and theaccumulation of plastic waste in the environment have resulted in extensiveresearch aimed at finding more sustainable alternatives to today’s plastics.In this work, bio-based and biodegradable polymers have been synthesizedusing free-radical polymerization in homogeneous and heterogeneoussystems. The polymers have been characterized with respect to chemicalstructure, thermal properties and degradation. This is a step towards thedevelopment of materials that are bio-based and biodegradable, ultimately toreduce the negative impact of plastic materials on the environment.It was found that bio-based α-methylene-γ-butyrolactone and α-methylene-γ-valerolactone (MeMBL) which exhibit similar chemical structures to fossilbasedmeth(acrylate) monomers, are capable of yielding polymers withsimilar or even superior properties compared to their fossil-basedcommodity counterparts. The differences in monomer reactivity affect thestructure of the copolymer which, in turn, influences the polymer properties,for instance, thermal behaviour (glass transition temperature). Theseproperties were later evaluated after the incorporation of MeMBL in thepolymeric shell of thermally expandable microspheres by free-radicalsuspension polymerization. Replacing fossil-based methyl methacrylate(MMA) with bio-based MeMBL resulted in partially bio-based thermallyexpandable microspheres (TEMs) where it was seen that the expansionproperties were affected as the expansion temperatures increased. It waseven possible to synthesize TEMs with a fully bio-based polymer shell with amuch higher expansion temperature window than TEMs with a fully fossilbasedpolymer shell.Free-radical ring-opening polymerization (rROP) has been used to synthesizedegradable polymers using cyclic ketene acetals (CKAs) which weresynthesized using a new more efficient synthesis route. Unlike traditionalring-opening polymerization, which results in linear polyesters, rROP of CKAsresults in branched polyesters. The degree of branching and introducing aside-group to the polymer chain influenced the polymer degradability wherethe presence of side-groups slowed the degradation significantly.The possibility to use these monomers in heterogeneous systems has beenevaluated by introducing CKA in the free-radical suspension polymerizationof microcapsules with a polymer shell from acrylonitrile (AN) and vinylacetate. However, their incorporation into the polymer backbone could notbe verified. This as the use of CKA in heterogeneous systems is challengingdue to their sensitivity towards hydrolysis and their low reactivity duringcopolymerization, especially toward acrylonitrile.
Förbrukning av ändliga fossilbaserade resurser och ackumulering avplastavfall i miljön har resulterat i en omfattande forskning som syftar till atthitta mer hållbara alternativ till dagens plaster.I detta arbete har biobaserade och biologiskt nedbrytbara polymerersyntetiserats med hjälp av fri-radikalpolymerisation i homogena ochheterogena system. Polymererna har karakteriserats med avseende påkemisk struktur, termiska egenskaper och nedbrytning. Detta är ett steg motutveckling av material som är biobaserade och biologiskt nedbrytbara ochsom i slutändan kan minska plastmaterialens negativa påverkan på miljön.De biobaserad monomererna α-metylen-γ-butyrolakton (MBL) och α-metylen-γ-valerolakton (MeMBL) som uppvisar liknande kemiska strukturersom fossilbaserade met(akrylat) monomerer, kan ge polymerer medliknande eller till och med överlägsna egenskaper jämfört med dessfossilbaserade råvarumotsvarigheter. Skillnaderna i monomerreaktivitetpåverkar strukturen hos sampolymeren, vilket i sin tur påverkarpolymeregenskaperna, till exempel termiskt beteende(mjukningstemperatur). Dessa egenskaper utvärderades senare efterinkorporering av MeMBL i polymerskalet av termiskt expanderbaramikrosfärer (TEMs) genom friradikal suspensionspolymerisation. Att ersättafossilbaserad metylmetakrylat med biobaserad MeMBL resulterade i delvisbiobaserade TEMs där man såg att expansionsegenskaperna påverkades närexpansionstemperaturerna ökade. Det var även möjligt att syntetisera TEMsmed ett helt biobaserat polymerskal med ett mycket högreexpansionstemperaturfönster än TEMs med ett helt fossilbaseratpolymerskal.Friradikal ringöppningspolymerisation (rROP) har använts för attsyntetisera nedbrytbara polymerer med cykliska ketenacetaler (CKA) somsyntetiserades med en ny mer effektiv syntesväg. Till skillnad fråntraditionell ringöppningspolymerisation, som resulterar i linjära polyestrar,resulterar rROP av CKA i grenade polyestrar. Graden av förgrening ochinförande av en sidogrupp till polymerkedjan påverkade polymerensnedbrytbarhet där närvaron av sidogrupper bromsade nedbrytningenavsevärt.Möjligheten att använda dessa monomerer i heterogena system harutvärderats genom att introducera CKA i fri-radikalsuspensionspolymerisation av mikrokapslar med ett polymerskal frånakrylnitril och vinylacetat. Inkorporering av CKA i polymerkedjan kundeemellertid inte verifieras. Detta eftersom användningen av CKA i heterogenasystem är utmanande på grund av deras känslighet för hydrolys och deraslåga reaktivitet under sampolymerisation, särskilt mot akrylnitril.
QC 20240222
Herein, we report the free-radical polymerization of the biobased alpha-methylene-gamma-butyrolactone and alpha-methylene-gamma-valerolactone, either into homopolymers or together with fossil-based (meth)acrylate monomers, methyl acrylate and methyl methacrylate in different ratios. The polymerization was thermally initiated by 2,2'-azobisisobutyronitrile or lauroyl peroxide to investigate their effect on the polymerization behaviors. Polymerizations were monitored by monomer conversion, and the final polymers were characterized with respect to molecular weight, composition, glass transition temperature, and thermal degradation. NMR showed significant differences in conversion rates of each monomer in the copolymerizations which suggest differences in reactivity ratios, sometimes to such an extent that the polymers exhibited a substantial compositional drift as corroborated by assessed thermal properties. Tailored T-g's and increased thermal stability were achieved by copolymerizing the lactones and the (meth)acrylates.
QC 20210910
Bio-based or partially bio-based thermally expandable microspheres were synthesized by suspension (co)polymerization of the bio-based monomer α-methylene-γ-valerolactone (MeMBL) together with acrylonitrile and/or methyl methacrylate to form expandable core/shell particles by encapsulating a hydrocarbon-based blowing agent. The core/shell polymers were characterized with respect to their chemical structure, thermal expansion and morphology. The obtained particles, thermally expandable microspheres (TEMs), showed an increasing onset expansion temperature with increasing content of MeMBL owing to the high glass transition temperature of PMeMBL. As a result, bio-based/partially bio-based TEMs are achieved with high thermal stability and expansion properties which can be tailored for various applications.
QC 20240320
QC 20240226
Microcapsules were synthesized by free-radical suspension polymerization using the cyclic ketene acetals (CKAs), 2-Methylene-1,3-dioxepane (MDO) and 5,6-Benzo-2-methylene-1,3-dioxepane (BMDO) together with acrylonitrile and vinyl acetate to encapsulate a blowing agent. The core/shell polymers were characterized with respect to their chemical structure, thermal expansion and morphology. SEM analysis confirmed the core/shell morphology of the particles which also showed a great encapsulation of the blowing agent by GC analysis. The incorporation of CKAs was difficult to confirm with structural analysis using NMR as there are many overlapping2peaks, however, the presence of BMDO in the system contributed to lower conversion of VAc and to a decreased thermal stability of the particle shell. Optimization of the polymerization system and a better control of the CKAs sensitivity to water are needed for a successful incorporation of CKAs.