4.4. SOFT CONDENSED MATTER

 

STUDIES ON RIGID ELECTROACTIVE POLYMERS

Mika Torkkeli, Ritva Serimaa, Kaija Jokela, M. Knaapila*, H. Eerikäinen*, R. Kuokka*, J. Ruokolainen*, O. Ikkala*, L. Horsburgh**, A. Monkman**, M. Jussila+ and G. ten Brinke++

Studies of polymer/amphiphile supermolecular complexes, which were initiated by our collaborators at the Helsinki University of Technology, were continued. Of particular current interest are conjugated polymers such as polyaniline (PANI) and polypyridine (PPY), which yield electric conductivity on doping. Conducting polymers are rigid or semi rigid and therefore insoluble. Addition of flexible side chains is an effective way to accomplish fusibilty and tractability. The accompanied self-organization brings forward intriguing possibilities in designing nanostructured electroactive components.

The emeraldine base (EB) polyaniline remains one the most studied of conducting polymer due to its price. Complex doping of the EB with Zn(DBS)2 was demonstrated using SAXS to give organized lamellar structure. Dopant concentration in excess of 0.5 mol/mol resulted in phase separation of Zn(DBS)2 rich phase. It is concluded that complexation takes place in the iminic nitrogen sites of EB.

While PPY's production output is measured in milligrams, pyridine containing polymers have potential as optical and electroactive materials such as blue/green emissive polymer LEDs and flat-panel displays. Mesophase structures were also obtained in methyl sulphonate protonated PPY(MSA) when complexed with octyl gallate (OG). Temperature dependent SAXS and WAXS measurements show phase behaviour dominated by possibly co-crystallized PPY(MSA) domains below 160° and ODT of the PPY(MSA)/OG mesophase at 160°.

* Department of Engineering Physics and Mathematics, Helsinki Univ. of Technology

** Department of Physics, Univ. Durham, UK

+ Panipol Oy, Finland

++ Dept. of Polymer Science and Materials Science Center, Univ. Groningen, The Netherlands

 

X-RAY SCATTERING STUDIES ON PROTON CONDUCTING MEMBRANES FOR FUEL CELLS

Kaija Jokela, Milja Karjalainen, Mika Torkkeli, Ritva Serimaa, Sakari Vahvaselkä, Veli Eteläniemi, M. Paronen* and F. Sundholm*

Structural investigations of proton conducting membranes have been continued by WAXS, SAXS and USAXS methods. The aim of this study is to develop new, inexpensive membrane materials for fuel cell applications requiring high proton conductivity and good mechanical, thermal and chemical stability. Two different matrix materials, poly(vinylidene fluoride), PVDF, and poly(vinylidene fluoride-co-hexafluoropropyl-ene), Kynar, have been used.

According to SAXS experiments Kynar-based membranes contain PVDF lamellae and ionic aggregates. The ionic peak that arises from ionic aggregates was observed at the SAXS intensity curve of humid membranes. The intensity of the ionic peak increases when the sample is metal labelled. According to fitting results the structure of the ionic aggregates of Kynar-based membranes is slightly different from the structure of the ionic aggregates of PVDF-based membranes. The behaviour of the lamellar period depended on the matrix material. When the hexafluoropropylene content was increased the lamellar period was changed strongly.

* Department of Chemistry, Univ. Helsinki

STRUCTURE OF POLYMER BASED PALLADIUM CATALYSTS

Kaija Jokela, Antti Kelloniemi, Ritva Serimaa, Veli Eteläniemi and K. Ekman*

The structure of polymer based palladium catalysts was studied by WAXS, SAXS and USAXS methods. The base material is polyethylene (PE) fibre which is irradiated with electrons and grafted with styrene, acrylic acid (AA) or 4-vinylpyridine (P4VP). Palladium is added to the material in the form of salt (Pd2+). To get catalytic active material palladium is reduced from Pd2+ to Pd0form using different activation reactions. Large differences in the catalytic activity of materials are observed. One aim of this study is to characterize the structure of the catalysts and to find out explanations for these differences.

According to WAXS experiments there are no other crystalline materials in Pd2+ form than PE. When palladium is reduced to Pd0 form, palladium crystallites are formed. P4VP grafted sample is an exception - there are no detectable palladium crystallites even on Pd0 form. Clear differences on the macrostructure of catalysts are observed by SAXS. The differences are due to different grafting materials and reduction processes. Polystyrene grafted and sulfonated PE contains ionic aggregates. At AA and P4VP grafted PE only a lamellar peak is observed. When the palladium is reduced to Pd0 form SAXS intensity contains features which might be associated to Pd crystallites.

* Smoptech Oy, Turku, Finland

INTERMOLECULAR ORDER IN MAIN CHAIN AND SIDE CHAIN LIQUID CRYSTALLINE POLYMERS

Sakari Vahvaselkä, Ritva Serimaa, Mika Torkkeli, Teemu Ikonen, K. Kaartinen*, T. Launne*, S. Niemelä* and F. Sundholm*

The structure and phase transitions of main chain and side chain liquid crystalline polymers were studied by WAXS, SAXS, DSC, and molecular modelling. Formation of several smectic and nematic phases as a function of temperature were observed in the side chain polymer with styrene backbone. In main chain polymers both the backbone chain and size groups participated in the same orthorombic lattice. For both types of polymers the degree of order varied with the length of the side chain.

* Department of Chemistry, Univ. Helsinki

X-RAY SCATTERING STUDIES OF POTATO STARCH

Teemu Ikonen, T. Väänänen*, Kaija Jokela, Ritva Serimaa, V.-M. Rokka+, L. Pietilä+ and E. Pehu**

Cultivated potatoes, wild species (Solanum acaule and Solanum brevidens) and hybrids between wild species and cultivated potatoes were studied by WAXS, SAXS and USAXS. The decrease in crystallinity and the increase in the average size of crystallites followed the dormancy in potato and the sprouting period. The structure of starch in hybrids of solanum tuberosum with species from Andes resembled more starch of the cultivated than that of the wild species.

* Department of Chemistry, Univ. Helsinki

+ Dept. of Plant Production, Univ. Helsinki

** Plant Production Research, Agricultural Research Centre of Finland

 

STRUCTURE OF WOOD CELLS IN NORWAY SPRUCE AND SCOTS PINE

Seppo Andersson, Matti-Paavo Sarén, Marko Peura, Kaija Jokela, Veli Eteläniemi, Ritva Serimaa, P. Saranpää*, E. Pesonen* and T. Paakkari

The structure of wood cells (tracheids) in Norway spruce and Scots pine was studied by means of X-ray scattering and optical microscopy. The distribution of microfibril angles (MFA) of the secondary cell wall layers S1, S2 and S3, the size (length and diameter) of cellulose crystallites and crystallinity were determined by means of wide angle X-ray scattering. These quantities were determined as a function of the year ring and height. Also the influence of fertilisation was studied by determining the microfibril angles of normal wood and fertilised wood. Furthermore, relationship between the average MFA and longitudinal shrinkage in Scots pine was studied. Porosity of the cell wall was studied by means of small angle and ultra small angle X-ray scattering. The average shape of tracheids and the thickness of cell walls were determined by analysing microscope pictures of transverse sections of wood samples by an imageprocessing program.

* Finnish Forest Research Institute METLA, Finland