Research groups

Contact Information

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00014 Helsingin yliopisto
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Research

tutkimus

Ionic Liquid Polymers

PILsIonic liquids are low-melting salts, usually consisting of large, unsymmetrical organic cation and small anion, which is usually inorganic. Ionic liquids are usually studied as solvents, since they have high solvating power, low vapor pressure and their properties can be easily varied by changing the anion. If Ionic liquid contains polymerizable group, such as methacrylate, they can be polymerized to yield polymerized ionic liquids (PILs).

PILs retain some properties of ionic liquids along with properties of traditional strong polyelectrolytes. Their solubility can be varied with changing the counter ion also, e.g. halide anion usually produces water-soluble PILs and tetrafluoroborate anion makes PILs water-insoluble. PILs can be used as a starting point in synthesis of block copolymers. In this study, micellization of copolymers consisting of hydrophobic PIL and hydrophilic, thermoresponsive poly(N-isopropyl acrylamide) (PNIPA) is studied. The formed micelles have a charged core, neutral corona and reversible thermal response in water, both in the micelle size and surface charge.

FunMat

Funmat logoCenter for Functional Materials (FUNMAT) is a national center of excellence in printed intelligence based at Åbo Akademi University and University of Helsinki .

FUNMAT is combining the expertise in chemistry, physics, polymer technology, paper coating and printing to develop functional materials and devices for printed intelligence. The multidisciplinary research is done in close collaboration with industry and our extensive collaboration network throughout the world.

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Supramolecular Amphiphilic Polymers

a dumbbell polymerNot much is known about the self-assembly or the rheological and amphiphilic properties of dumbbell polymers. Star-star dumbbell polymers will be synthesized, aiming for amphiphilic systems that have functional characteristics, for example temperature- or pH-dependent behavior. Star arm composition and length as well as the length of the linker polymer will be varied. Poly(ethylene oxide) (PEO) will be used as a linker polymer due to its water-solubility. Several types of star arms will be polymerized via atom transfer radical polymerization (ATRP), mainly acrylates and methacrylates. The rheological and amphiphilic properties of the novel star-star dumbbell polymers will be thoroughly investigated.

This project is a part of the ESPOM (Electrochemical Science and Technology of Polymers and Membranes including Biomembranes) graduate school.

New polymers prepared from natural oils for coatings and paper and 
packaging systems

structureThere is an increasing demand for sustainable development to replace  fossil based products with novel renewable materials. Hence, new  innovations, products, and materials with enhanced performance and   specific functional properties in harmony with the principles of  sustainable development are of great importance.
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Modular and Programmable Polymeric Platform for Controlled Ocular Drug  Delivery

structure of hyaluronanHyaluronic acid (HA) is a naturally occurring anionically charged linear polysaccharide. This  polymer is present in the extracellular matrix of all vertebrates, especially in synovial fluid, cartilage, vitreous humour and skin. It has various important functions in the body, including cell proliferation and migration, increasing the resilience of cartilage and participation in healing processes in damaged skin.
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New Cellulose Derivatives

celluloseCellulose is the most abundant natural polymer and a very promising raw material available at low cost for the preparation of various functional polymers. It has many attractive properties such as hydrophilicity, biocompatibility, biodegradable, stereoregularity, multichirality, reactive hydroxyl groups and the ability to form superstructure. Although it has many useful properties it lacks the solubility and processability that most synthetic polymers possess. Before it can be used in polymer applications, cellulose needs to be modified, usually this involves reaction of the hydroxyl groups to give cellulose esters and ethers. Cellulose esters and ethers are used e.g. in coatings, films, membranes, controlled-release systems, and pharmaceuticals.
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Double-Thermoresponsive Macromolecules

thermoresNew polymer architectures containing poly(dimethylaminoethyl methacrylate) (PDMAEMA) and poly(ethylene oxide) (PEO) have been synthesized. PDMAEMA is a polymer which can show phase separation at low and high temperature (UCST-type transition at low temperatures and LCST-type transitions at elevated temperatures). E.g. heteroarm star-shaped polymers consisting of four / six arms of PDMAEMA and two arms of PEO were prepared and investigated in buffered solutions. When multivalent counterions are present, they form micelles at low and high temperatures. PEO acts then as the solubilizing part. Also dumbbell-shaped polymers consisting of star-shaped PDMAEMA as compact associating groups at the termini of a PEO spacer containing the same constituents were prepared for use in advanced hydrogel applications.
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Hybrid Nanocomposites from Clay

In our research montmorillonite has been used to prepare nanocomposites and
“smart”nanocontainers. The approach in composite research is to modify the
clay with different polymers to improve mixing and/or exfoliation of the
clay platelets. The main objective is the improvement of mechanical
properties of composites. The mechanical properties of composites have been
studied by dynamic mechanical thermal analysis (DMTA).

Montmorillonite clay is used to prepare “smart” nanocontainers for
“intelligent” surface materials. The fundamental idea is the production of
star polymers with a clay core. These star polymers could then be used as
smart nanocontainers for different agents, depending on the application. A
multi-level self-healing approach will combine –within one system –several
damage prevention and reparation mechanisms, which will be activated
depending on type and intensity of the environmental impact. Several types
of substrates will be studied like metals, plastics and composites. Aluminum
and magnesium alloys and steel will be in main focus. A video on a successful project: http://www.sintef.no/Projectweb/MUST/

Stimuli-responsive associative polymers and hydrogels

PNIPAMAssociative polymers are of industrial importance owing to their adjustable rheological properties for example in paints, cosmetics formulations or pharmaceutical as well as medical applications. Particularly interesting are the stimuli-responsive systems of associating polymers in which free standing gels transform to free-flowing liquids or vice versa. To obtain such systems water-soluble polymers modified with a small number of hydrophobic groups are often used. Enhanced viscosity and reversible gelling behaviour originate from transient intermolecular associations between the hydrophobic groups.
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Stimuli-responsive polymers based on calix[4]arenes and crown ethers

starpolymerOver the course of time, research on molecules capable of hosting low molar mass guests has been gaining momentum and interest in the scientific community. While numerous complexes have been extensively studied, providing necessary information on structure and strength of the non-covalent binding, preparation of polymeric systems comprising these units has not been a feasible task.
While derivatives of crown ethers and their application in polymeric systems have been an actively pursued subject for many years, calix[4]arenes have been predominantly used as initiator cores for the preparation of star polymers via ATRP.They can also be embedded into the main chain or as a side group . Our group has recently reported on the successful preparation of photo-switchable polymers comprising exclusively of calix[4]arenes: poly(azocalix[4]arene)s (Fig. 1).
Combining different architectures of (co)polymers, along with the hosting abilities of calix[4]arenes and also crown ethers may lead to the development of very interesting materials capable of specific recognition of ions and/or small molar mass compounds. By tuning the character of blocks within the (co)polymers one can induce thermo-, pH-, or photosensitivity and thus influence the physicochemical properties of the system upon different external stimuli.
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Star polymers as hosts for low molecular weight compounds

starpolymerAmphiphilic star block copolymers are a new and interesting alternative for binding and solubilizing various low molecular weight hydrophobic molecules. In solution, amphiphilic star copolymers can exist either as unimolecular micelles or associate to micelle-like aggregates. At the moment, two different kinds of strategies to utilize star block copolymers are studied in our laboratory. Amphiphilic star-shaped block copolymers with functional cores are prepared by controlled radical polymerization. One project is aiming to produce novel optically active materials. In this case, the core of the star should have the ability to complex low molecular weight compounds with non-linear optical properties. The complexation of the star polymers and the effect of the complexation on the properties of the guest molecule will be studied. The other project aims to prepare stimulus-responsive amphiphilic star polymers to be used in controlled release applications. The compatibility and binding capability of the polymers with various fungicides will be determined and the release of these activates in response to external stimuli will be carried out.

Controlled Radical Polymerisation

radical
The synthesis of materials with controlled compositions, architectures and functionalities has been of great scientific interest in recent years, owing to the development of controlled radical polymerization methods. These methods allow the syntheses of tailored polymers and molecular composites with well-defined structures and functionalities, giving control over the macroscopic properties.

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Globules and Mesoglobules in Aqueous Media

globules

Colloidal stability of particles formed by thermosensitive homopolymers PNIPAM, PVCL and PVME and polyelectrolytes in dilute aqueous solutions have been investigated in water under thermodynamically poor conditions. To obtain colloidally stable aggregates, mesoglobules, no stabilizing agent was added. The mesoglobules were shown to be homogeneous spheres similar to the globules of individual macromolecules and have a very narrow size distribution. The origin of colloidal stability is studied now.

Gold Nanoparticles

gold

Monolayer-protected clusters (MPC) of metal nanoparticles constitute a rapidly emerging field due to the very specific electronic, optoelectronic, and catalytic properties. MPC is a core-shell nanocomposite composed of a metal core and a shell ranging from small organic compounds to macromolecules.

Recent studies involve functional gold nanoparticles coated with calix[4]arene compounds that offer the nanoparticles supramolecular properties.

Environmentally Responsive Polymers

envinroment

Environmentally responsive polymers are a fascinating group of water-soluble polymers. These polymers are sensitive to an external stimulus in the environment and have a specific respond on that. The respond might be, for example, a volume change of a hydrogel or some other conformational changes in the polymer structure that may induce the pursued respond. Such systems are based on well designed polymers that have a particular functionality which is sensitive to the available impulse.

Fluorinated Polymeric Surfactants

fluorinated

Polymers that contain atomic fluorine in or along the backbone exhibit many desirable physical properties, such as strong surface activity, enhanced chemical resistance and high thermal stability. Their interfacial properties in liquid systems play an important role in their practical application to food, paint, cosmetic and medical emulsions, as well as in polymerisation, solvent extraction and other processes. Polymeric surfactants are often more surface active and form more stable emulsions compared with smaller molecular weight compounds.

NMR Spectroscopy of Polymers

NMR

Advanced NMR applications are used to clarify the relation between the chemical structure and physical properties of macromolecules. Various liquid and solid state NMR methods are used in the research projects in our laboratory.

Wood Polymers

woodWood consists mainly of polymers. The physical structure of wood is a complex composite of cellulose, hemicelluloses, lignin and low-molecular-mass extractives. The major wood component, cellulose, is a linear high molecular mass polymer built up of anhydro-D-glucopyranose units linked by b(1-4) glycosidic linkages (Fig. 1). Hemicelluloses are branched low-molecular-mass compounds. Lignin is a branched heterogeneous aromatic polymer formed of phenylpropane units linked together mainly by b-O-4 arylether linkages.

New Dissolution Processes for Cellulose

woodWood cellulose needs to be dissolved prior e.g. textile fiber production. Cellulose is insoluble in conventional solvents, but novel dissolution processes have been developed for cellulose dissolution. Aqueous solvent systems, such as NaOH-urea-water or ZnO-NaOH-water and many ionic liquids dissolve cellulose. Ionic liquids, salts with low melting points (<100 °C), have interesting properties, such as negligible vapor pressure, low flammability and potential recyclability in industrial processes. Ionic liquids we use are able to dissolve cellulose easily with heating or even at room temperature. Along with the water based solvent systems they offer an alternative for the environmentally costly viscose process, which is a commonly used method for cellulose dissolution.
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