Paper is a result of our scientific engagement in the field of hyperbranched polymers, which, because of the highly branched structure and a large number of functional groups, show unique properties that make them interesting for various applications. The influence of synthetic conditions on the complex structure and molar-mass characteristics of hyperbranched polyesters together with the findings, allowing a thorough understanding of the structure-property relationship are reviewed in detail. Additionally, the paper summarizes the type of application of hyperbranched polyesters, ranging from industrial to high-tech areas.
COBISS.SI-ID: 4487194
Necrosis and ethylene-inducing peptide 1–like (NLP) proteins constitute a superfamily of proteins produced by plant pathogenic bacteria, fungi, and oomycetes. Many NLPs are cytotoxins that facilitate microbial infection of eudicot, but not of monocot plants. Here, we report glycosylinositol phosphorylceramide (GIPC) sphingolipids as NLP toxin receptors. Plant mutants with altered GIPC composition were more resistant to NLP toxins. Binding studies and x-ray crystallography showed that NLPs form complexes with terminal monomeric hexose moieties of GIPCs that result in conformational changes within the toxin. Insensitivity to NLP cytolysins of monocot plants may be explained by the length of the GIPC head group and the architecture of the NLP sugar-binding site. We unveil early steps in NLP cytolysin action that determine plant clade-specific toxin selectivity. Two Departments of the NIC participated in this work, demonstrating fruitful cooperation between both research groups. In addition, this work reveals interdisciplinary engagement of the research group of the Department of Polymer Chemistry and Technology in research activities similarly as is proposed in this programme.
COBISS.SI-ID: 6289178
We report on a method for preparation of well-defined synthetic polypeptides by ring-opening polymerization of ?-amino acid N-carboxyanhydrides (NCA) initiated by a hydroxyl group. To overcome the issue of slow initiation by hydroxyl group, an acid catalyst was used in initiation step to catalyze opening of the NCA ring by the hydroxyl group and to simultaneously suppress further chain propagation by protonation of the formed amine group. In this way, we have separated slow initiation from the fast chain propagation, since such a combination leads to poorly defined products, and instead performed them in a successive manner. Only after completion of the initiation, the propagation was started by the addition of a base to deprotonate the ammonium group. This method was successfully applied for the synthesis of homopolypeptides by using alcohol as an initiator as well as polypeptide-based block copolymers by using poly(ethylene glycol) or poly(styrene) macroinitiator terminated with the hydroxyl group. This approach not only expands the pool of possible initiators, but also significantly facilities the preparation of polypeptide-based hybrid polymers.
COBISS.SI-ID: 6168602
High internal phase emulsions of water in cyclooctene stabilized by sorbitan monooleate (Span 80) were cured by ring-opening metathesis polymerization to release fully open macroporous polymer foams wherein the surfactant was covalently incorporated into the poly(cyclooctene) strands via chain transfer reactions. In this work, we have shown that stable high-internal phase emulsions (HIPEs) can be prepared by using an appropriate surfactant, which upon curing yield the highly porous polymeric foams (polyHIPEs) in which the surfactant is covalently incorporated into the pore surface. In this way, the surface of the pores can be in-situ modified to increase hydrophilicity of the pore surface. Experiences with different approaches to modification of the surface of the scaffold are of utmost importance for preparation of the desired and optimal surface functionality of the scaffold, which will be suitable for cell attachment and proliferation.
COBISS.SI-ID: 37876997
MOF@polyHIPE hybrid foams were prepared using a metal salt-free technique, wherein metal–organic frameworks were in situ generated from the CuO and ZnO nanoparticles through the secondary recrystallization. The MOF phase within the hybrid polyHIPEs as disclosed herein, exhibited superior micropore accessibility and structure hydrostability. These results were the follow up work on the previously reported MOF@polyHIPE hybrid foams (Macromolecular Rapid Communications, 2015, 36, 1605-1611), where we observed the micropore clogging and MOF stability issues. In the present work MOFs were not incorporated directly into the emulsion, therefore they were not exposed to water and other emulsion components that affect the emulsion stability. The nanoparticle-to-MOF transformation has proven to be an effective technique for preparing MOF@polyHIPE hybrid materials with a high MOF stability and content.
COBISS.SI-ID: 6072090
In the past few years extracellular vesicles called exosomes have gained huge interest of scientific community since they show a great potential for human diagnostic and therapeutic applications. However, an ongoing challenge is their accurate size characterization and quantification due to lack of reliable characterization techniques. Therefore, our work focused on a method development to size-separate, characterize and quantify small amounts of exosomes by asymmetrical flow field-flow fractionation (AF4) technique coupled to a multi-detection system (UV and multi-angle light-scattering, MALS). Batch DLS and NTA analyses of unfractionated exosomes were also conducted in order to evaluate their shape, internal structure and their number density.
COBISS.SI-ID: 5754138
We report on the synthesis of highly transparent and UV-absorbing PMMA/ZnO nanocomposites prepared by hydrolysis of a ZnO precursor, i.e. the A-b-(AB) diblock copolymer: poly(methyl methacrylate)-block-poly(methyl methacrylate-co-(zinc methacrylate acetate)) = PMMA-b-P(MMA-co-ZnMAAc), synthesized by RAFT polymerization. The zinc content in the block copolymers was in the range from 3 to 13 wt. %. The PMMA block provides inherent compatibility with the PMMA matrix, whereas the second block, P(MMA-co-ZnMAAc) with zinc ions, acts as a polymeric precursor for the formation of ZnO nanoparticles. The amphiphilic block copolymer self-organizes in THF and THF/H2O in ordered nanostructures and thereby influences the nanoparticle formation during the hydrolysis of the precursor block copolymer with KOH. The ZnO nanoparticles were rod shaped with the lengths up to 80 nm and a diameter of 14 nm and were redispersible in THF. Dispersions in THF and thin films of PMMA/ZnO nanocomposite exhibit excellent transparency in the visible range and good absorption in the UV range below 400 nm.
COBISS.SI-ID: 5295642
In this scientific paper, a new process for the production of nanocellulose from the selected cellulose-containing natural materials has been described. The liquefaction reaction, using glycols and mild acid catalyst (methane sulphonic acid), was applied to four model materials, i.e. cotton linters, spruce wood, eucalyptus wood and Chinese silver grass. The process contains only four steps, i.e. the milling, glycolysis reaction, centrifugation and final rinsing with an organic solvent. The nanocrystalline cellulose recovery was between 56 and 75 %. The crystallinity index was greater than those of the starting materials due to liquefaction of lignin, hemicelluloses and amorphous cellulose. The final product was a stable, highly concentrated nanocrystalline cellulose suspension in the organic or aqueous medium. The liquid residue obtained after liquefaction of the cotton linters contained significant amounts of levulinic acid and various sugar types. The described process of NNC isolation was granted with the International Patent No. WO2015/088451.
COBISS.SI-ID: 38446853
HIPE templating was also used for preparation of ?-conjugated macroporous foams based on 1,3-diethynylbenzene, which after the UV-radiation show the UV / VIS and photoluminescent response. Foams with such electronic structure show a great potential for applications in opto-electronics or for photocatalytic applications and will be the subject of further research in our Department.
COBISS.SI-ID: 5523482
Asymmetrical flow field-flow fractionation (AF4) technique coupled to a multi-angle light-scattering (MALS) detector with embedded dynamic light scattering (DLS) module was introduced to study the size-characteristics and shape of soft particles of various size and type. A range of passage flow velocities at the detector coupled to AF4 at which accurate hydrodynamic size can be extracted from the DLS in flow mode was studied since the particles subjected to a longitudinal flow exhibit not only the Brownian motion due to diffusion, but also the translational movement. In addition, the impact of the rate of the passage flow at the detector in AF4 system on the shape of artificial vesicles was studied by MALS. For comparison, the conventional batch DLS and static light-scattering (SLS) experiments without prior sample separation by size were performed. From a combination of batch and flow light scattering results we concluded that the passage flow velocities at the detector used in this study have no significant impact on the shape of spherical vesicles, however, the flow DLS experiments give accurate hydrodynamic radius (Rh) only at the lowest investigated flow rate, that is 0.2 mL/min. With increasing detector flow rate, the error in the accuracy of the Rh determination rapidly increases. The error in Rh depends solely on the particle size regardless of the soft particle type.
COBISS.SI-ID: 6240794