Resumen de Photosensitive polymers and their applications
This thesis focuses on synthesis of novelphotosensitive polymers and theirsuccessive application in photo-triggered microcapsules preparation. In particular, the project aims at incorporation of photosensitive moiety -Donor-Acceptor Stenhouse adducts (DASA) within polymeric matrixes. Mainly two distinct approaches were followed in this thesis. Firstapproachinvolves incorporation of DASA within the side chain of commercially available polymers, specificallyfive types ofpoly(styrene-co-maleic anhydride) (SMA) with different molecular weights and molar ratio compositions. As prepared modified polymers were then applied to obtain microcapsulescontaining active agents, such as perfumes provided by Procter & Gamble Company. Second approach involves modification of a methacrylate (2-(tert-Butylamino)ethyl methacrylate (TBA)) monomer with DASA and then its subsequent application for microcapsules preparation by interfacial polymerization method.Both approaches lead to our final goal which is preparation of capsules withphototriggeredcontrolled release of encapsulated cargo.
XVIVIISummaryThis thesis focuses on synthesis of novelphotosensitive polymers and theirsuccessive application in photo-triggered microcapsules preparation. In particular, the project aims at incorporation of photosensitive moiety -Donor-Acceptor Stenhouse adducts (DASA) within polymeric matrixes. Mainly two distinct approaches were followed in this thesis. Firstapproachinvolves incorporation of DASA within the side chain of commercially available polymers, specificallyfive types ofpoly(styrene-co-maleic anhydride) (SMA) with different molecular weights and molar ratio compositions. As prepared modified polymers were then applied to obtain microcapsulescontaining active agents, such as perfumes provided by Procter & Gamble Company. Second approach involves modification of a methacrylate (2-(tert-Butylamino)ethyl methacrylate (TBA)) monomer with DASA and then its subsequent application for microcapsules preparation by interfacial polymerization method.Both approaches lead to our final goal which is preparation of capsules withphototriggeredcontrolled release of encapsulated cargo.In order to reach the objectives, the following studies were performed:I.Preparation of DASA precursor;II.SMA modification with DASA moieties to obtain photoactive polymers (SCIII);III.Studies of SCIII polymersbehaviour upon light exposure;IV.Application of SCIII polymers to obtain membrane and capsules. Subsequent characterization of prepared material; V.Modification of TBAwith DASA moieties and its characterization;VI.Preparation of photosensitive polyacrylates capsules containing DASA moieties within its matrix and their performance evaluation.During first year of this PhD thesis, an optimization of the synthesisof 5-(furan-2-ylmethylene)-2,2-dimethyl-1,3-dioxane-4,6-dionewas carried out. This molecule serves as DASAprecursor required for themodification ofthe polymeric matrix. Optimization of preparation procedure,previously reported in the literature,was successfully performed. Results obtained from this part provide a more robust andapractical method to gain a high yield of 5-(furan-2-ylmethylene)-2,2-dimethyl-1,3-dioxane-4,6-dionein water without the need of a catalyst, making the process more economically efficient, less tedious, sustainable and environmentally friendly.In the second stage,themodifications of thefivecommercially available SMA copolymers were studied. Within this task, first the maleic anhydride group of the SMA copolymers weremodified with 2°amines. Despite the fact that, the reaction between maleic anhydride group and primary amines is known in the literature; investigation on the reaction conditions was required to get poly(styrene-co-maleimide)s (SCII). Then, the purified SCIIswere used inthe reaction with previously synthesised DASA –precursor to create copolymers with photosensitive properties (SCIII).In the third part, thephotosensitive performance of the final SCIII polymers was exhausting investigated. The negative type T photochromism as well as the solvatochomism of DASA molecules wereretainedafter its incorporation withinSMAstructure. It was conjectured that the mechanism of the photoswitching waspreserved after polymer modification,as described previously in the literature. The alternation of the photoisomerization kinetics between parent DASA and modified polymerscontaining DASA moieties in their structureswas investigatedanddeeplyanalysed. Two separate models were applied: Eyring and Arrhenius to describechanges inarate of chemical transition against temperature.In the fourth stage,membranes and series of microcapsules containing SCIII polymers were fabricated.The membranes were prepared in order to facilitate the investigation of the SCIII polymers physicochemicalproperties. It was assumed that SCIII membranes will mimic the behaviour of the photosensitive microcapsulesshell. Thus, the membranes were obtained by solvent evaporation method.Four techniques were used to preparethecapsules: 1) phase inversion precipitation; 2) emulsion crosslinking of partially modified SCIII copolymer (DASA modified polymer, molar ratio ST-styrene, MA-maleic anhydride, MI-maleimide; 4ST : 1MA : 2MI; 3) SMA/SCIII emulsion precipitation in different non-solvents; 4)emulsion crosslinking of SCIII with SMA blend. Membranes modification upon light exposure were analysed by means of AFM, CAand FT-IR analysis. SCIII polymers capsules behaviourupon light exposure were analysed by means of ESEM, optical microscope and GC analysis.In the fifth stage synthesis Acrylate/DASA moleculewas performed, in order to use it for microcapsule shell preparation employing a protocol developed by scientists from P&G Company. Indeed, during the next step of the thesis the Acrylate/DASA moleculewas used together with 2 other acrylate resins (provided by P&G) for capsules preparation. Furthermore, during the sixth stage of the PhD thesis, surfaces of acrylate capsules provided by P&G Company were modified with DASA precursor. Obtained capsules were characterized by meansXIXof optical microscope and dynamic headspace–thermal desorption (DHS–TD) combined with gas chromatography–mass spectrometry (GC–MS).
