INFLUENCE OF POLYMER MIXTURE ON THE PROPERTIES OF POROUS POLY(DIVINYL ADIPATE-CO-PENTAERYTHRITOL TETRAKIS(3-MERCAPTOPROPIONATE))

V tem diplomskem delu predstavljamo vpliv več dejavnikov na velikost in porazdelitev por v polimernem materialu pripravljenem iz emulzije z visokim deležem notranje faze. Tako smo spreminjali volumski delež vodne faze in topila, spreminjali smo hitrost mešanja pri pripravi emulzije nato pa smo jo starali. Polimerne materiale smo okarakterizirali z VEM (vrstičnim elektronskim mikroskopom) in optičnim mikroskopom, nato pa s primernim računalniškim programom obdelali slike in izmerili pore. Kot monomera pri emulziji voda v olju (v/o) smo uporabili divinil adipat in tetrakis(3-merkaptopropionat). Uporabljen porogen v našem raziskovalnem delu je bil toluen, kot surfaktant pa smo uporabili kombinacijo Span 65 in PEL 121. Za aktivacijo polimerizacije smo uporabili fotoiniciator Irgacure 819. Polimerizacija poteče po mehanizmu tiol-en kemije. Preučevali smo vpliv dodatka vodne faze na velikost por in ugotovili, da pri 85 vol.% dodane vodne faze nastanejo največje pore v tem polimeru in dobimo tipično poliHIPE strukturo. Prav tako smo spreminjali delež toluena, ker dodajanje porogena vpliva na velikost por v polimeru. Z večanjem dodanega porogena smo povečali pore in zaznali največje pore pri dodatku 50 vol.% porogena. Nato smo spreminjali še hitrost mešanja emulzije od 50 do 250 obratov/min (s korakom 50). Iz rezultatov slik SEM-a in optičnega mikroskopa opazimo, da so pore bistveno večje pri emulzijah, ki smo jih mešali pri nižjih obratih (50 obratov/min, 50 TOPLA), kot pa pri višjih. Največje pore smo izmerili pri 50 (Tvodne faze = 40 °C) TOPLA, najmanjše pa pri 200 obratih/min. S staranjem emulzije smo opazili, da se kapljice vodne faze s časom večajo, za kar sta odgovorna koalescenca in Ostwaldovo zorenje. Ugotovimo, da se vsem pripravljenim emulzijam s časom (do 48h) velikosti kapljic povečajo, dokler emulzija ne postane popolnoma nestabilna in se fazi ločita, kar se zgodi po dveh dneh.In the graduation thesis the influences of some factors on the cell pore size in porous polymer material which was prepared from high internal phase emulsions templating were shown. The volume of aqueous phase, solvent and stirring rate were changed. Polymers were characterized via scanning electron microscopy and optical microscop. Emulsions containing divinyl adipate and tetrakis(3-mercaptopropionate) as the monomers were prepared. Suitable solvent was toluene, while the surfactant was used mixture of Span 65 and PEL 121. Than we added photoiniciator and photopolymerisation was carried out. Polymerisation mechanism occurring is thiol-ene step-growth polymerisation. The effects of adding aqueous phase to a solution of monomers were studied. The optimal aqueous content of HIPE was 85 vol. %, meaning that in this case the droplet size increased the most. Also the volume of toluene was changed, because the porogen has an effect on pore size. The optimal toluene content in HIPE was 50 vol. %. The rate of stirring was found to be between 50 rpm to 250 rpm. Emulsions were analyzed with optical microscope and polymers with scanning electron microscope and both gave us comparable results. The size of internal phase droplets increased with decreasing stirring rate and the same occurred with pores in polymer. Pore enlargement was measured at 50 rpm and heated internal phase to 40°C and the reduction of stirring to 200 rpm. Finaly we studied the effects of emulsions aging. Internal phase droplets size increase with aging of emulsion mainly due to Ostwald rippenig and coalescence. We concluded that emulsions which were aged up to 48 hours were stable but after that phases separated

POROUS HYBRID MATERIALS IN SYSTEM MONOMER/TiO

V magistrskem delu smo se lotili sinteze poroznega hibridnega materiala sestavljenega iz sistema monomer-propoksiliran trimetitol propan triakrilat in delcev TiO2. Hibridni material smo pripravili s polimerizacijo emulzije z visokim deležem notranje faze tipa voda v olju, kateri smo v zunanjo fazo primešali delce TiO2 . Hibridni material smo nato sintrali. Ugotovili smo, da na stabilnost emulzije ne vpliva narava in količina dodanega surfaktanta PEL 121 ampak emulzijo stabilizira le disperzno sredstvo BYK 118. Prav tako smo iz eksperimentalnega dela ugotovili, da na stabilizacijo emulzije vpliva masno razmerje delci:monomer. Kadar smo v emulzijo dodali dvakrat več monomera kot delcev, je bila ta stabilna tudi po dodatku 80 vol.% vodne faze, material je imel odprto celično strukturo. Z višanjem količine delcev (delci:monomer na 1:1, 2:1) pa emulzije pri dodatkih visokih deležev vodne faze (več kot 70 vol.%) postajajo vedno manj stabilne njihova celična struktura pa je bolj zaprta. Pomemben dejavnik za stabilizacijo sistema monomer-TiO2 je tudi velikost delcev. Ugotovili smo, da z delci velikosti 20 nm težje stabiliziramo HIP emulzijo, kot pa z delci velikosti 200 nm. Dobljene porozne hibridne materiale smo nato sintrali na temperaturi 1150 ⁰C pri temperaturnem koraku 0,5 ⁰C na minuto. Izkazalo se je, da se hibridnim materialom z nižjim deležem delcev tipična poliHIPE struktura poruši. Medtem, ko pa se tistim materialom z višjim deležem delcev (delci:monomer 2:1) struktura poruši verjetno zaradi že predhodno manj stabilnega hibridnega materiala. Vsi sintrani materiali so izboljšali svoje mehanske lastnosti, saj so vsi postali trdnejši . Struktura je ostala podobna poliHIPE materialu kadar smo dodajali manjšo količino delcev glede na monomer in kadar smo dodajali nižje vsebnosti notranje faze (manj kot 80 vol.%). V tem delu smo sintetizirali hibridni material iz sistema monomer-TiO2, nadalje smo ga sintrali in tako bolj ali manj uspešno dobili porozno keramično matrico, katere morfologija je nakazovala podobnost s hibridnim materialom. Tako delo še v znanstveni literaturi ni bilo opisano.In this master thesis, we deal with the synthesis of porous hybrid materials consisting of sistem monomer-TiO2 particles. Propoxylated trimetitol propane triacrylate was used as monomer. The hybrid materials were prepared by the polymerization of the high internal phase emulsion type water-in-oil. To the external phase particles of TiO2 were added. The hybrid material was then sintered. It was found that the stability of the emulsion is not affected by the nature and quantity of added surfactant PEL 121. Emulsions were stabilised with dispersing agent BYK 118. Also, we have established that the stabilization of the emulsion is affected by the weight ratio of particles: monomer. When the emulsion was added twice as much monomer as particles, it was stable even after the addition of 80 vol.% of the aqueous phase and the material had an open cellular structure. With increasing amounts of particles (particles: monomer at 1:1, 2:1), and with adding high proportions of the aqueous phase (more than 70 vol.%) emulsions became less stable and their cellular structure was more closed. An important factor for the stabilization of the system the monomer-TiO2 is also the size of the particles. We have found that it is more difficult to stabilize the HIP emulsion using particles with diameter of 20 nm, than with particles with diameter of 200 nm. The resulting porous hybrid materials were then sintered at a temperature of 1150⁰C with a temperature step 0,5⁰C per minute. Typical polyHIPE structures in hybrid materials were collapsed by adding lower mass of particles. Structures of sintered hybrid materials with a higher proportion of particles (particle:monomer of 2:1) were collapsed likely due to the previously less stable hybrid material. All sintered materials had improved mechanical properties, as they all became harder. In this work we synthesized a hybrid material from the system monomer-TiO2, we have further sintered and thus more or less successfully obtained a porous ceramic matrix whose morphology indicates similarities with the hybrid material. Such work in the scientific literature has not yet been described

Creating micro structure in polyHIPEs through syneresis, hypercrosslinking and grafting

V doktorski disertaciji smo pripravili polimere stirenskega tipa z več nivojsko poroznostjo. Dobro definirano porozno strukturo smo dosegli s kombiniranjem različnih tehnik za uvedbo poroznosti v polimere. S polimerizacijo kontinuirne faze emulzije z visokim deležem notranje faze smo ustvarili makro porozne polimere s povezovalno odprto celično poliHIPE strukturo. Mikro poroznost smo dosegli s Friedel-Craftsovo reakcijo hiperzamreženja in s sineretsko fazno separacijo z uporabo mešanice topil. Več nivojska porazdelitev velikosti por je izjemno pomembna pri uporabi polimernih materialov v pretočnih sistemih, kjer makro pore omogočajo konvektivni prenos snovi in zmanjšujejo povratne tlake, medtem ko manjše mezo in mikro pore vplivajo na povečanje specifične površine. Visoko porozne poli(stiren-ko-divinilbenzen) polimere smo pripravili s polimerizacijo kontinuirne faze emulzije z visokim deležem notranje faze. Monolite smo sintetizirali s prosto radikalsko in RAFT (reverzna adicijsko-fragmentacijska polimerizacija s prenosom verige) polimerizacijo. V obeh primerih polimerizacij so imeli polimeri tipično poliHIPE strukturo. Polimere smo nato hiperzamrežili z radikalskim iniciatorjem di-tert-butil-peroksidom in tako pridobili mikro in mezo pore, ter posledično vplivali na dvig BET specifične površine (3-4-kratno povišanje). Prav tako je na mikro strukturo poliHIPE materialov vplivala vrsta polimerizacije. Z RAFT polimerizacijo smo dobili 4-5-krat višje specifične površine ne hiperzamreženih poliHIPE materialov kot pri uporabi proste radikalske polimerizacije, kar kaže na porast formiranja mikro por pri RAFT zamreženju. Poli(stiren-ko-4-vinilbenzil klorid-ko-divinilbenzen) poliHIPE materiale s tipično poliHIPE odprto celično strukturo smo sintetizirali pri različnih stopnjah začetnega zamreženja (2, 5 in 10%). Z dodatkom stirena v monomerno mešanico smo dosegli redčenje funkcionalnih skupin in tako študirali vpliv redčenja na potek Friedel-Craftsove reakcije hiperzamreženja. S hiperzamreženjem smo v makro porozne poliHIPE materiale uvedli mikro pore in dosegli visoke BET specifične površine (do 731 m2/g). Pri dodatku 57-63 mol % STY je bilo redčenje funkcionalnih skupin preveliko, da bi bilo hiperzamreženje še učinkovito, specifične površine so drastično padle, kar kaže na pomanjkanje mikro por. Graftirali smo glicidil metakrilat s površine makro poroznih poli(4-vinilbenzil klorid-ko-divinilbenzen) monolitov pripravljenih z radikalsko polimerizacijo kontinuirne faze emulzije. Z namenom povišanja specifične površine smo visoko porozne poliHIPE materiale hiperzamrežili s Friedel-Craftovo reakcijo in jih nadalje funkcionalizirali z razvejanim tris(2-aminoetil)aminom. Proste amino skupine razvejanega amina smo uporabili za imobilizacijo RAFT reagenta, ki je bil primeren za graftiranje glicidil metakrilata s površine. Z graftiranjem s površine poliHIPE materialov z vezanim RAFT reagentom smo dobili visoko gostoto glicidil metakrilatnih molekul na površini. Graftiranje smo izvedli le na hiperzamreženih materialih, saj so ti dosegli večje konverzije pri reakciji z aminom in RAFT reagentom, zaradi večje dostopnosti reaktivnih mest. Učinkovitost reakcije graftiranja smo potrdili z gravimetrijo, elektronsko vrstično spektroskopijo in infrardečo spekroskopijo. Dinamična mehanska analiza je pokazala, da smo z RAFT polimerizacijo izboljšali mehanske lastnosti poli(4-vinilbenzil klorid-ko-divinilbenzen) poliHIPE materialom. V drugem delu doktorske disertacije smo uporabili sineretsko fazno separacijo pri sintezi poli(4-vinilbenzil klorid-ko-divinilbenzen) zrn s suspenzijsko polimerizacijo. Monomerno fazo smo razredčili s toluenom ali z mešanico topil toluen/heksan. Mikro pore so se formirale zaradi mikrosineretske fazne separacije ob prisotnosti toluena, ki je dobro topilo za stirenske tipe polimerov. Zrna smo hiperzamrežili in s tem uvedli v material nove mikro pore, ki so posledica nastanka novih metilenskih povezav. S tem smo dosegli visokeWithin the doctoral dissertation, styrene-based polymers with multilevel porosity were prepared. A well-defined porous structure was achieved by combining different techniques to introduce porosity into the polymers. By polymerizing the continuous phase of a high internal phase emulsion, macroporous polymers with an open cell interconnected polyHIPE structure were formed. Micropores were obtained using a Friedel-Crafts hypercrosslinking reaction, and by syneretic phase separation using a mixture of solvents. Multilevel pore size distribution is advantageous when using polymeric materials in flow systems where macropores allow convective mass transfer and reduce back pressures, while smaller meso- and micropores increase the specific surface area. Highly porous poly (styrene-co-divinylbenzene) polymers were prepared by polymerizing the continuous phase of a high internal phase emulsion. Monoliths were synthesized by free radical and RAFT (reversible addition-fragmentation chain transfer) polymerization. In both polymerization types, the polymers had a typical polyHIPE structure. The polymers were then hypercrosslinked with the radical initiator di-tert-butyl peroxide to obtain micro- and mesopores, and consequently to raise the BET specific surface area (3 to 4 fold increase). The microstructure of the polyHIPE materials was also affected by the type of polymerization. Compared to the polymers prepared using free radical polymerization, the specific surface areas of non-hypercrosslinked polyHIPE materials prepared with RAFT polymerization were 4-5 times higher, which indicates increased formation of micropores in the case of RAFT crosslinking mechanism. Furthermore, poly (styrene-co-4-vinylbenzyl chloride-co-divinylbenzene) polyHIPE materials with a typical open cellular polyHIPE structure were prepared at different initial crosslinking degrees (2, 5 and 10%). The addition of styrene to the monomer mixture dilutes the functional groups and enables the study of the effect of dilution on the Friedel-Crafts hyperlinking reaction. The hypercrosslinking reaction introduces micropores into the macroporous polyHIPE materials which results in high BET specific surfaces (up to 731 m2/g). At 57-63 mol% of STY the dilution of the functional groups is too intense to enable effective hypercrosslinking which results in a drastic drop in specific surface areas and a lack of micropores, compared to samples with higher concentrations of functional groups. In continuation, glycidyl methacrylate was grafted from the surface of macroporous poly (4-vinylbenzyl chloride-co-divinylbenzene) monoliths which were prepared by the radical polymerization of the continuous phase of the high internal phase emulsion. In order to increase the specific surface area the highly porous (80% porosity) polyHIPE materials were hypercrosslinked by Friedel-Craft reaction and further functionalized with branched tris (2-aminoethyl) amine. The free amino groups of the branched amine were used to immobilize a suitable RAFT agent for glycidyl methacrylate grafting from the surface. High surface density of the glycidyl methacrylate molecules on the surface was obtained by surface grafting of the polyHIPE materials with bound RAFT reagent. Grafting was performed only on the hypercrosslinked materials, as these achieved higher conversions in the reaction with the amine and RAFT reagent, due to the greater accessibility of the reactive sites. The efficiency of the grafting reaction was confirmed by gravimetry, scanning electron microscopy and infrared spectroscopy. The RAFT polymerization also improved the mechanical properties of the poly (4-vinylbenzyl chloride-co-divinylbenzene) polyHIPE materials. In the second part of the doctoral work, syneretic phase separation was used as the tool for porosity induction in the synthesis of poly (4-vinylbenzyl chloride-co-divinylbenzene) beads using suspension polymerization. The monomer phase was diluted with toluene or with

Influence of functional group concentration on hypercrosslinking of poly(vinylbenzyl chloride) PolyHIPEs

With the aim to study the influence of monomer ratio in poly(high internal phase emulsions) (polyHIPEs) on the polymer network architecture and morphology of poly(vinylbenzyl chloride-codivinylbenzene-co-styrene) after hypercrosslinking via the internal Friedel–Crafts process, polyHIPEs with 80% overall porosity were prepared at three different initial crosslinking degrees, namely 2, 5, and 10 mol.%. All had typical interconnected cellular morphology, which was not affected by the hypercrosslinking process. Nitrogen adsorption and desorption experiments with BET and t-plot modelling were used for the evaluation of the newly introduced nanoporosity and in combination with elemental analysis for the evaluation of the extent of the hypercrosslinking. It was found that, for all three initial crosslinking degrees, the minimum amount of functional monomer, 4-vinylbenzyl chloride, was approximately 30 mol.%. Hypercrosslinking of polymers with lower concentrations of functional monomer did not result in induction of nanoporosity while the initial crosslinking degree had a much lower impact on the formation of nanoporosity

Reusable Pd-PolyHIPE for Suzuki–Miyaura Coupling

Palladium was immobilized on a highly porous copolymer of 4-vinylpyridine and divinylbenzene (polyHIPE─poly(high internal phase emulsion)) using palladium(II) acetate to obtain PolyPy-Pd with 6.1 wt % or 0.57 mmol Pd/g. The immobilized catalyst was able to catalyze the coupling of iodobenzene and phenylboronic acid in ethylene glycol monomethyl ether/water (3:1) within 4 h at rt and complete conversion was observed when 2.5 mol % of Pd per PhI was used. The reaction tolerated a wide range of substituents on the aromatic ring. Iodobenzene derivatives with electron-withdrawing substituents showed higher reactivity, while the opposite was true for the phenylboronic acid series. The polyHIPE-supported Pd catalyst was also used for the direct conversion of phenylboronic acid to biphenyl through an iodination/coupling reaction sequence. The recyclability of the heterogeneous catalyst was also optimized, and by finding a suitable combination of solvents for the loading of Pd, the reaction, and the isolation of the product, the solid-supported catalyst was completely regenerated and used in the next reaction with the same activity

Novel hypercrosslinking approach toward high surface area functional 2-hydroxyethyl methacrylate-based polyHIPEs

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