Browsing by Subject "POLYMERS"

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  • Zhang, Chao; Vehkamäki, Marko; Pietikäinen, Mika; Leskelä, Markku; Ritala, Mikko (2020)
    Novel area-selective molecular layer deposition (AS-MLD) of polyimide (PI) on Cu versus native SiO2 was studied. By use of 1,6-diaminohexane (DAH) and pyromellitic dianhydride (PMDA) as precursors, PI films can be selectively deposited on the Cu surface at 200-210 degrees C with a rate around 7.8 A/cycle while negligible growth takes place on SiO2. The selectivity was successfully demonstrated also on Cu/SiO2 patterns at 200 degrees C; after 180 MLD cycles, around 140 nm thick PI was deposited on Cu regions while
  • Scopetani, Costanza; Chelazzi, David; Cincinelli, Alessandra; Esterhuizen-Londt, Maranda (2019)
    In the last few years, several studies have investigated microplastics (MPs) in marine ecosystems, but data monitoring and assessing the occurrence in freshwater environments are still scarce. The present study aims to investigate the occurrence, distribution, and chemical composition of MP pollution in Vesijärvi lake and Pikku Vesijärvi pond close to the city of Lahti (Finland) in winter. Sediment, snow, and ice core samples were collected near the shore of these two aquatic systems. MPs were analysed and identified by a non-destructive method using Fourier transform infrared spectroscopy (FTIR) 2D imaging. The mean concentrations of MPs detected in sediment, snow, and ice samples were 395.5 ± 90.7 MPs/kg, 117.1 ± 18.4 MPs/L, and 7.8 ± 1.2 MPs/L, respectively. FTIR results showed the predominant abundance of microplastics, such as polyamides (up to 53.3%), polyethylene and polypropylene (up to 17.1%), and natural fragments such as cellulose (up to 45.8%) and wool (up 18.8%) in the same size range. The potential release of MPs arising from stormwaters and sport and recreational activities was evidenced.
  • Soikkeli, Maiju; Kettunen, Mikko I.; Nivajärvi, Riikka; Olsson, Venla; Ronkko, Seppo; Laakkonen, Johanna P.; Lehto, Vesa-Pekka; Kavakka, Jari; Heikkinen, Sami (2019)
    Magnetic resonance imaging examinations are frequently carried out using contrast agents to improve the image quality. Practically all clinically used contrast agents are based on paramagnetic metals and lack in selectivity and specificity. A group of stable organic radicals, nitroxides, has raised interest as new metal-free contrast agents for MRI. Their structures can easily be modified to incorporate different functionalities. In the present study, a stable nitroxide TEEPO (2,2,6,6-tetraethylpiperidin-1-oxyl) was linked to a glucose moiety (Glc) to construct a water-soluble, potentially tumor-targeting compound with contrast-enhancing ability. The ability was assessed with in vivo MRI experiments. The constructed TEEPO-Glc agent proved to shorten the T-1 relaxation time in tumor, while the T-1 time in healthy brain tissue remained the same. The results indicate the potential of TEEPO-Glc as a valuable addition to the growing field of metal-free contrast enhancement in MRI-based diagnostics.
  • Pale, Ville; Nikkonen, Taru; Vapaavuori, Jaana; Kostiainen, Mauri; Kavakka, Jari; Selin, Jorma; Tittonen, Ilkka; Helaja, Juho (2013)
  • Nyman, Leo; Kestila, Antti; Porri, Paavo; Pudas, Marko; Salmi, Mika; Silander, Rudolf; Miikkulainen, Ville; Kaipio, Mikko; Kallio, Esa; Ritala, Mikko (2021)
    Many fields, including the aerospace industry, have shown increased interest in the use of plastics to lower the mass of systems. However, the use of plastics in space can be challenging for a number of reasons. Ultraviolet radiation, atomic oxygen, and other phenomena specifically associated with space cause the degradation of polymers. Here we show a path toward creation of space-grade components by combining additive manufacturing (AM) and atomic layer deposition (ALD). Our method produced ALD Al2O3 coated thermoplastic parts suitable for space applications. The highlight of this work is a significant reduction in outgassing, demonstrated using residual gas analyzer (RGA) sampling. Compared to uncoated parts, the ALD Al2O3 coating decreased the outgassing of polyether ether ketone (PEEK), acrylonitrile butadiene styrene (ABS), polycarbonate (PC), and nanodiamond-doped polylactide (ND-PLA) by 46%, 49%, 58%, and 65%, respectively. The manufacturing method used in this work enables the use of topology optimization already in the early concept creation phase. The method is ideally suited for spacecraft applications, in which the volume and mass of parts is critical, and could also be adapted for in-space manufacturing. (c) 2021 American Society of Civil Engineers.
  • Siren, Heli; El Fellah, Sandra (2019)
    Microemulsion gels were synthetized from macadamia, linseed, olive, walnut, rapeseed, sesame, and coconut oils and frying oil made from sunflower, palm, and rapeseed oils. The gels were similar as polyacrylamide-based gels with exception of replacing dodecyl sulfate with vegetable oils. The gels were modified with celluloses, cotton, or lignin to make the emulsions sustainable for water purification. They were used to compare sorption properties when they were used as solid-phase adsorbents in isolation of steroids from water. Hydrophobicity features of the gels were compared by detecting adsorption and extraction efficiency of nonpolar androstenedione, testosterone, and progesterone, which exist in wastewater and drinking water. Quantification was done with partial filling-micellar electrokinetic chromatography with 29.5 mM sodium dodecyl sulfate-3.4 mM sodium taurocholate as the micelle and 20 mM ammonium acetate (pH 9.68) as the electrolyte. UV-detection was used. Methanol was the best eluent for extraction of steroids from gels. The highest recoveries were from frying oil and rapeseed oil gels modified with celluloses. They also possessed the best floating properties on water surface. Lignin modified gels were too hydrophilic, when in touch with water they filled up with water. They also had the lowest capacity.
  • Tenkanen, Maija; Pitkänen, Leena (2019)
    The asymmetric flow field-flow fractionation (AF4) method was developed for cationic cellulose derivatives. AF4 is the method of choice especially for high-molar mass samples, which are challenging to characterize with conventional chromatographic techniques such as size-exclusion chromatography (SEC). The cationic charge of macromolecules also complicates the size-based separations where no interaction between the analytes and the column stationary phase (SEC) or membrane (AF4) should occur. However, many column matrices and membranes carry negative charge and thus preventing interactions between cationic analytes and negatively charged separation support should be taken into consideration when doing method development. In this study, two eluent compositions, neutral and acidic, were tested for AF4 separation of cationic hydroxyethyl celluloses with varying charge densities. The eluent composition with a pH below the isoelectric point of regenerated cellulose membrane, which was used in this AF4 study, enabled the size-based separation with close to 100% analysis recovery. Macromolecular parameters (molar mass and radius of gyration) and conformation were investigated by coupling a multi-angle light scattering detector and differential refractometer to the AF4 system.
  • Wiktorowicz, Szymon; Tenhu, Heikki; Aseyev, Vladimir (2013)
  • Wang, Shiqi; Wannasarit, Saowanee; Figueiredo, Patricia; Molinaro, Giuseppina; Ding, Yaping; Correia, Alexandra; Casettari, Luca; Wiwattanapatapee, Ruedeekorn; Hirvonen, Jouni; Liu, Dongfei; Li, Wei; Santos, Hélder A. (2021)
    In this study, a rationally designed nanocomposite (BUDPDA@MAP) composed of polydopamine (PDA) nanoparticle and anti‐inflammatory drug budesonide (BUD) encapsulated in a pH‐responsive endosomolytic polymer (poly(butyl methacrylate‐co‐methacrylic acid) grafted acetalated dextran, denoted by MAP), is proposed. The uniform nanocomposite is prepared using a microfluidic device. At low endosomal pH (5.5), MAP destabilizes the endosomal membranes for the cytoplasmic delivery of PDA, and releases BUD simultaneously, resulting in a greater reactive oxygen species scavenging capability than both the free drug and PDA alone. The combined therapeutic efficacy from PDA and BUD also leads to a successful macrophage phenotype switch from pro‐inflammatory M1 to anti‐inflammatory M2.
  • Hahn, Lukas; Maier, Matthias; Stahlhut, Philipp; Beudert, Matthias; Flegler, Vanessa; Forster, Stefan; Altmann, Alexander; Toeppke, Fabian; Fischer, Karl; Seiffert, Sebastian; Boettcher, Bettina; Luehmann, Tessa; Luxenhofer, Robert (2020)
    Amphiphilic block copolymers that undergo (reversible) physical gelation in aqueous media are of great interest in ditIerent areas including drug delivery, tissue engineering, regenerative medicine, and biofabrication. We investigated a small library of ABA-type triblock copolymers comprising poly(2-methyl-2-oxazoline) as the hydrophilic shell A and different aromatic poly(2-oxazoline)s and poly(2-oxazine)s cores B in an aqueous solution at different concentrations and temperatures. Interestingly, aqueous solutions of poly(2-methyl-2-oxazoline)-block-poly(2-phenyl-2-oxazine)-block-poly(2-methyl-2-oxazoline) (PMeOx-b-PPheOzi-b-PMeOx) undergo inverse thermogelation below a critical temperature by forming a reversible nanoscale wormlike network. The viscoelastic properties of the resulting gel can be conveniently tailored by the concentration and the polymer composition. Storage moduli of up to 110 kPa could be obtained while the material retains shear-thinning and rapid self-healing properties. We demonstrate three-dimensional (3D) printing of excellently defined and shape-persistent 24-layered scaffolds at different aqueous concentrations to highlight its application potential, e.g., in the research area of biofabrication. A macroporous microstructure, which is stable throughout the printing process, could be confirmed via cryo-scanning electron microscopy (SEM) analysis. The absence of cytotoxicity even at very high concentrations opens a wide range of different applications for this first-in-class material in the field of biomaterials.
  • Ren, Hao; Qiu, Xing-Ping; Shi, Yan; Yang, Peng; Winnik, Francoise M. (2019)
    Azopyridines (AzPy) act as light-sensitive groups that undergo reversible cis-trans isomerization upon UV irradiation, as hydrogen-bond acceptors, and as ionizable moieties. The kinetics of the thermal cis- to trans-AzPy deactivation are slow except when the Py nitrogen is H-bonded or cationic. The properties of AzPy were used here to control the phase transition of aqueous solutions of alpha-azopyridine-omega-n-dodecyl-poly(N-isopropylacrylamides) (C12-PN-AzPy) with the molar mass (M-n) ranging from 5800 to 19 700 g mol(-1). The C12-PN-AzPy polymers form cationic star-micelles in solutions of pH 3 and flower-micelles in neutral and basic solutions. This diversity of micelle morphology underlies the temperature-, pH- and UV-irradiation-driven phase transition of aqueous C12-PN-AzPy solutions as demonstrated by turbidimetry, H-1 NMR spectroscopy, and microcalorimetry. Unlike azobenzene, the commonly used photoresponsive moiety to actuate amphiphilic polymers, AzPy can affect the thermoresponsive behavior of polymers in response to three orthogonal triggers: pH, through changes in ionization; light, via trans-cis photoisomerization; and time, from hours to a few ms, via the kinetics of the dark cis-trans relaxation. The study leads the way to responsive sensors or actuators in the form of aqueous fluids, hydrogels, or films by the application of light and changes of temperature and pH in permutable sequences.
  • Knaapila, M.; Fonseca, S. M.; Stewart, B.; Torkkeli, M.; Perlich, J.; Pradhan, S.; Scherf, U.; Castro, R. A. E.; Burrows, H. D. (2014)
  • Ghafourisaleh, Saba; Popov, Georgi; Leskela, Markku; Putkonen, Matti; Ritala, Mikko (2021)
    Because of its high conductivity and intrinsic stability, poly(3,4-ethylenedioxythiophene (PEDOT) has gained great attention both in academic research and industry over the years. In this study, we used the oxidative molecular layer deposition (oMLD) technique to deposit PEDOT from 3,4-ethylenedioxythiophene (EDOT) and a new inorganic oxidizing agent, rhenium pentachloride (ReCl5). We extensively characterized the properties of the films by scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy (XPS), energy-dispersive X-ray spectroscopy (EDS), Raman, and conductivity measurements. The oMLD of polymers is based on the sequential adsorption of the monomer and its oxidation-induced polymerization. However, oMLD has been scarcely used because of the challenge of finding a suitable combination of volatile, reactive, and stable organic monomers applicable at high temperatures. ReCl5 showed promising properties in oMLD because it has high thermal stability and high oxidizing ability for EDOT. PEDOT films were deposited at temperatures of 125-200 degrees C. EDS and XPS measurements showed that the as-deposited films contained residues of rhenium and chlorine, which could be removed by rinsing the films with deionized water. The polymer films were transparent in the visible region and showed relatively high electrical conductivities within the 2-2000 S cm(-1) range.
  • Otsuka, Issei; Zhang, Xuewei; Winnik, Francoise M. (2019)
    Aqueous dispersions of nanogels that respond to switches in environmental pH and/or temperature by changes in their hydrodynamic radius (R-h) and/or zeta-potential are prepared by reversible addition-fragmentation chain-transfer (RAFT) polymerization-induced thermal (70 degrees C) self-assembly (PITSA) of N-isopropylacrylamide (NIPAM) in the presence of a poly(methacrylic acid) (PMAA)-substituted macromolecular chain transfer agent and a cross-linker. Photochromic spiropyran (SP) moieties are coupled to the carboxylic acid groups of the nanogels. Upon UV irradiation, the neutral SP isomerizes to the zwitterionic merocyanine (ME) form. Upon UV light irradiation, microgels formed by assembly of SP nanogels undergo a collective motion toward the UV-light source.
  • Näkki, Pinja; Eronen-Rasimus, Eeva Liisa; Kaartokallio, Hermanni; Kankaanpää, Harri; Setälä, Outi; Vahtera, Emil; Lehtiniemi, Maiju (2021)
    Resistant to degradation, plastic litter poses a long-term threat to marine ecosystems. Biodegradable materials have been developed to replace conventional plastics, but little is known of their impacts and degradation in marine environments. A 14-week laboratory experiment was conducted to investigate the sorption of polycyclic aromatic hydrocarbons (PAHs) to conventional (polystyrene PS and polyamide PA) and bio-based, biodegradable plastic films (cellulose acetate CA and poly-L-lactic acid PLLA), and to examine the composition of bacterial communities colonizing these materials. Mesoplastics (1 cm(2)) of these materials were incubated in sediment and seawater collected from two sites in the Gulf of Finland, on the coast of the highly urbanized area of Helsinki, Finland. PS sorbed more PAHs than did the other plastic types at both sites, and the concentration of PAHs was consistently and considerably smaller in plastics than in the sediment. In general, the plastic bacterial biofilms resembled those in the surrounding media (water and/or sediment). However, in the sediment incubations, the community composition on CA diverged from that of the other three plastic types and was enriched with Bacteroidia and potentially cellulolytic Spirochaetia at both sites. The results indicate that certain biodegradable plastics, such as CA, may harbour potential bioplastic-degrading communities and that PAH sorption capacity varies between polymer types. Since biodegradable plastics are presented as replacements for conventional plastics in applications with risk of ending up in the marine environment, the results highlight the need to carefully examine the environmental behaviour of each biodegradable plastic type before they are extensively introduced to the market. (C) 2020 The Author(s). Published by Elsevier B.V.
  • Tiainen, Tony; Myllymäki, Teemu T. T.; Hatanpää, Timo; Tenhu, Heikki; Hietala, Sami (2019)
    Colloidal stability of negatively charged nanodiamonds (ND) has been realized with the help of double hydrophilic block copolymers poly(ethylene oxide)-block-poly(dimethylaminoethyl methacrylate)-dodecyl (PEO-bPDMAEMA-C12). The polymers were synthesized through RAFT polymerization of DMAEMA with a PEO macromonomer carrying trithiocarbonate and dodecyl end-groups. The NDs and the polymers were complexed by mixing them in different ratios. In addition to the amount of polymers, the effect of the detailed structure of the polymer was of interest and thus, also polymers with different lengths of the PEO-block were synthesized, as well as a block copolymer without the dodecyl end-group. The composition of the polymer, as well as the complexation conditions were varied to find the route to stable nanoparticles. The optimized complexation method gave colloidally stable ND particles with positively charged PDMAEMA coronas. The colloids were stable at room temperature and also in saline solutions up to 0.154 M NaCl.
  • Kirila, Tatyana; Smirnova, Anna; Aseyev, Vladimir; Tenkovtsev, Andrey; Tenhu, Heikki; Filippov, Alexander (2021)
    The behavior of star-shaped six-arm poly-2-alkyl-2-oxazines and poly-2-alkyl-2-oxazolines in aqueous solutions on heating was studied by light scattering, turbidimetry and microcalorimetry. The core of stars was hexaaza [2(6)] orthoparacyclophane and the arms were poly-2-ethyl-2-oxazine, poly-2-isopropyl-2-oxazine, poly-2-ethyl-2-oxazoline, and poly-2-isopropyl-2-oxazoline. The arm structure affects the properties of polymers already at low temperatures. Molecules and aggregates were present in solutions of poly-2-alkyl-2-oxazines, while aggregates of two types were observed in the case of poly-2-alkyl-2-oxazolines. On heating below the phase separation temperature, the characteristics of the investigated solutions did not depend practically on temperature. An increase in the dehydration degree of poly-2-alkyl-2-oxazines and poly-2-alkyl-2-oxazolines led to the formation of intermolecular hydrogen bonds, and aggregation was the dominant process near the phase separation temperature. It was shown that the characteristics of the phase transition in solutions of the studied polymer stars are determined primarily by the arm structure, while the influence of the molar mass is not so significant. In comparison with literature data, the role of the hydrophobic core structure in the formation of the properties of star-shaped polymers was analyzed.
  • Siirila, Joonas; Karesoja, Mikko; Pulkkinen, Petri; Malho, Jani-Markus; Tenhu, Heikki (2019)
    Soft poly(N-vinylcaprolactam) (PNVCL) based nanogels were prepared and surface-decorated with gold nanoparticles (AuNPs). The applicability of the hybrid nanogels (PNVCL-AuNPs) as carriers for low molar mass substances was of special interest. AuNPs protected with a mixture of 11-azidoundecanothiol and 11-mercaptoundecanoic acid were bound to propargyl functionalized PNVCL based nanogels. Acidic groups on the surfaces of AuNPs and PNVCL based nanogels stabilize the particle dispersions against precipitation above the phase transition temperature of PNVCL. Both the neat PNVCL nanogels and the PVCL-AuNPs shrink upon heating the dispersions. Even though the AuNPs are mainly located in the soft surface layer of the nanogels, the PNVCL-AuNPs respond to visible light as well as to radio-frequency (RF) irradiation by shrinking due to the AuNPs acting as nanoheaters. Interactions of linear PNVCL, PNVCL nanogels and PNVCL-AuNPs with two fluorescent probes were studied as function of increasing temperature. Once bound to the polymer the fluorescent probe may or may not be released from it, depending on its polarity and water solubility. Presence of AuNPs changed the release behavior of the water soluble charged fluorescent probe from the nanogels.
  • Herlan, Claudine Nicole; Sommer, Katharina; Weis, Patrick; Nieger, Martin; Bräse, Stefan (2021)
    Peptoids, or poly-N-substituted glycines, are characterised by broad structural diversity. Compared to peptides, they are less restricted in rotation and lack backbone-derived H bonding. Nevertheless, certain side chains force the peptoid backbone into distinct conformations. Designable secondary structures like helices or nanosheets arise from this knowledge. Herein, we report the copper-catalysed alkyne-azide cycloaddition (CuAAC) of macrocycles to form innovative tube-like tricyclic peptoids, giving access to host-guest chemistry or storage applications. Different linker systems make the single tubes tuneable in size and enable modifications within the gap. An azobenzene linker, which is reversibly switchable in conformation, was successfully incorporated and allowed for light-triggered changes of the entire tricyclic structure.
  • Fliervoet, Lies A. L.; Lisitsyna, Ekaterina S.; Durandin, Nikita A.; Kotsis, Ilias; Maas-Bakker, Roel F. M.; Yliperttula, Marjo; Hennink, Wim E.; Vuorimaa-Laukkanen, Elina; Vermonden, Tina (2020)
    Combining multiple stimuli-responsive functionalities into the polymer design is an attractive approach to improve nucleic acid delivery. However, more in-depth fundamental understanding how the multiple functionalities in the polymer structures are influencing polyplex formation and stability is essential for the rational development of such delivery systems. Therefore, in this study the structure and dynamics of thermosensitive polyplexes were investigated by tracking the behavior of labeled plasmid DNA (pDNA) and polymer with time-resolved fluorescence spectroscopy using fluorescence resonance energy transfer (FRET). The successful synthesis of a heterofunctional poly(ethylene glycol) (PEG) macroinitiator containing both an atom transfer radical polymerization (ATRP) and reversible addition-fragmentation chain-transfer (RAFT) initiator is reported. The use of this novel PEG macroinitiator allows for the controlled polymerization of cationic and thermosensitive linear triblock copolymers and labeling of the chain-end with a fluorescent dye by maleimide-thiol chemistry. The polymers consisted of a thermosensitive poly(N-isopropylacrylamide) (PNIPAM, N), hydrophilic PEG (P), and cationic poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA, D) block, further referred to as NPD. Polymer block D chain-ends were labeled with Cy3, while pDNA was labeled with FITC. The thermosensitive NPD polymers were used to prepare pDNA polyplexes, and the effect of the N/P charge ratio, temperature, and composition of the triblock copolymer on the polyplex properties were investigated, taking nonthermosensitive PD polymers as the control. FRET was observed both at 4 and 37 degrees C, indicating that the introduction of the thermosensitive PNIPAM block did not compromise the polyplex structure even above the polymer's cloud point. Furthermore, FRET results showed that the NPD- and PD-based polyplexes have a less dense core compared to polyplexes based on cationic homopolymers (such as PEI) as reported before. The polyplexes showed to have a dynamic character meaning that the polymer chains can exchange between the polyplex core and shell. Mobility of the polymers allow their uniform redistribution within the polyplex and this feature has been reported to be favorable in the context of pDNA release and subsequent improved transfection efficiency, compared to nondynamic formulations.