Nanoszerkezetű amfifil kotérhálók és gélek = Nanostructured amphiphilic conetworks and gels

A nanoszerkezetű amfifil kotérhálók és gélek területén az OTKA pályázat támogatásával több új eredményt is sikerült elérnünk. Új szintézis módszereket dolgoztunk ki, és tanulmányoztuk a kotérhálók összetétele és szerkezete közötti összefüggéseket. Polimetakrilsav alapú kotérhálókat védőcsoportot tartalmazó monomerek alkalmazásával sikerült előállítanunk oly módon, hogy a védőcsoport eltávolítása a kialakult térhálós anyagban történt. Blokk-kopolimerek térhálósításával modell kotérhálókat állítottunk elő, és felderítettük az összetétel, szerkezet és tulajdonságok közötti alapvető összefüggéseket. Szupramolekuláris kapcsolódással kétféle új kotérhálót szintetizáltunk. Az egyik esetben mágneses térre érzékeny termikusan reverzibilis szupramolekuláris gélt állítottunk elő, a másik esetben pedig a fizikai gél kiváló nanotemplátnak bizonyult nanopórusos szervetlen anyagok (pl. SiO2 és TiO2) létrehozására. Kiemelkedő fontosságúnak tartjuk, hogy - tudomásunk szerint a világon elsőként - sikerült felderíteni a kotérhálók összetétetele és nanofázis szerkezetű morfológiája közötti összefüggéseket. A kotérhálók nanofázis szerkezetét kihasználva ezüst és rézsó tartalmú nanohibrideket sikerült előállítanunk. Poli(N-vinil-imidazol) tartalmú amfifil kotérhálókról bebizonyosodott, hogy hatékony nehézfémion megkötő anyagok. Biológiai vizsgálataink szerint pedig mind a sejtletapadás, mind pedig a fehérjeadszorpció jól szabályozható a kotérhálók szerkezeti paramétereivel. | In the field of nanostructured amphiphilic conetworks and gels several new fundamental results have been achieved by us with the support of the OTKA fund. New synthesis methods were developed and relationships between the conetwork composition and structure were investigated. Successful synthesis of poly(methacrylic acid) containig conetworks was achieved by using monomers with suitable protecting groups followed by the removal of these groups after polymerization. Model conetworks were made from block copolymers and their fundamental composition - structure - properties relationships were explored. Two types of conetworks were synthesized by supramolecular linkages to obtain magnetic field responsive thermally reversible supramolecular gels and unique nanotemplates for nanoporous inorganic materials (e.g. SiO2 and TiO2). It is surpassingly important, that to the best of our knowledge the first time in the world, the successful exploration of the relationship between the composition and the nanophase structured morphology of conetworks was carried out by us. Utilizing the nanophase separated structure, it was possible to synthesize novel silver and copper containing nanohybrid materials. It was proved that poly(N-vinyl imidazole) amphiphilic conetworks are excellent heavy metal chelating materials. It was also shown by our studies that both cell adhesion and protein absorption could be controlled easily by structural parameters of the amphiphilic conetworks

Thermally Responsive Amphiphilic Conetworks and Gels Based on Poly(N‑isopropylacrylamide) and Polyisobutylene

Novel amphiphilic conetworks (APCN) consisting of thermoresponsive poly(N-isoproplyacrylamide) (PNiPAAm) cross-linked by hydrophobic methacrylate-telechelic polyisobutylene (MA-PIB-MA) were successfully synthesized in a broad composition range. The resulting PNiPAAm-l-PIB conetworks (“l” stands for “linked by”) were obtained by radical copolymerization of NiPAAm with MA-PIB-MA in tetrahydrofuran, a cosolvent for all the components. Low amounts of extractables substantiated efficient network formation. The composition dependent two glass transition temperatures (Tg) by DSC analysis indicate microphase separation of the cross-linked components without mixed phases. It was found that the PNiPAAm-l-PIB conetworks are uniformly swellable in both water and n-hexane; i.e., these new materials behave either as hydrogels or as hydrophobic gels in aqueous or nonpolar media, respectively. The uniform swelling in both polar and nonpolar solutes indicates cocontinuous (bicontinuous) phase morphology. The equilibrium swelling degrees (R) depend on composition, that is, the higher the PIB content, the lower the R in water and the higher in n-hexane. The PNiPAAm phase keeps its thermoresponsive behavior in the conetworks as shown by significant decrease of the swelling degree in water between 20 and 35 °C. The lower critical solubility temperature (LCST) values determined by DSC are found to decrease from 34.1 °C (for the pure PNiPAAm homopolymer) to the range of 25–28 °C in the conetworks, and the extent of the LCST decrease is proportional with the PIB content. Deswelling-swelling, i.e., heating–cooling, cycle indicates insignificant hysteresis in these new thermoresponsive materials. This indicates that PNiPAAm-l-PIB conetworks with predetermined and thermoresponsive swelling behavior can be designed and utilized in several advanced applications on the basis of results obtained in the course of this study

One-pot synthesis of block-copolyrotaxanes through controlled rotaxa-polymerization

The aqueous reversible addition fragmentation chain-transfer (RAFT) copolymerization of isoprene and bulky comonomers, an acrylate and an acrylamide in the presence of methylated β-cyclodextrin was employed for the first time to synthesize block-copolyrotaxanes. RAFT polymerizations started from a symmetrical bifunctional trithiocarbonate and gave rise to triblock-copolymers where the outer polyacrylate/polyacrylamide blocks act as stoppers for the cyclodextrin rings threaded onto the inner polyisoprene block. Statistical copolyrotaxanes were synthesized by RAFT polymerization as well. RAFT polymerization conditions allow control of the composition as well as the sequence of the constituents of the polymer backbone which further effects the CD content and the aqueous solubility of the polyrotaxane

Atom transfer radical polymerization with protein-conjugated catalysts : easy removal of copper traces and controlled radical polymerizations in protein nanoreactors

Atom transfer radical polymn. (ATRP) catalysts conjugated to globular, fluorescent, and cage-like proteins are reported. Bovine serum albumin served as functional handle to remove the copper contg. catalyst effectively from soln. Moreover, fluorescent proteins rendered the catalyst traceable by simple fluorescence measurements. The conjugation chem. also allows the attachment of the catalyst to the inside wall of the thermosome, a protein cage from the class of chaperonins, thus confining the polymn. into a nanoscale reaction space in this protein nanoreactor. Such systems allow to drastically reduce the residual copper content in polymers synthesized by ATRP and allow to synthesize well-defined polymers, because conducting ATRP in a nanoreactor enhances the degree of control of aq. ATRP

Star and Hyperbranched Polyisobutylenes via Terminally Reactive Polyisobutylene-Polystyrene Block Copolymers

Unique, highly branched polyisobutylenes (PIB) were prepared via quasiliving carbocationic copolymerization of isobutylene and styrene (St) monomers. The junction points were formed by Friedel-Crafts self alkylation of PSt segments by the carbocationic chain ends. First, linear PIB was prepared with reactive chain ends. This was reacted with St monomer to form PIB-b-PSt AB, and PSt-b-PIB-b-PSt ABA type triblock copolymers with reactive carbocationic chain ends. The terminal carbonations react with the phenyl group of the polystyrene end-segments of the block copolymers leading to chain coupling, and thus PIB star polymers in the case of AB and hyperbranched PIB from ABA block copolymers. The resulting branched polymers were characterized and the branch formation was confirmed by gel permeation chromatography (GPC) and proton nuclear magnetic resonance spectroscopy (1H NMR)