Sähköisesti johtavan polymeerin sulamispisteen säätäminen eutektisilla seoksilla

Conducting polymers have been studied in order to find new functional materials and materials for soft electronics. However, these polymers are poorly soluble and generally infusible because of the stiff polymer backbone. In this work it has been studied, whether the melting temperature of polyaniline can be tuned using resorcinol. The motivation of the study is that lower melting point would allow the melt processing of polyaniline. The aim of the present work is to study the solubility of polyaniline in resorcinol and the phase behaviour of polyaniniline-resorcinol mixture. Samples of polyaniline and resorcinol with different weight fractions were made. It was observed that homogeneous and fusible polyaniniline-resorcinol mixture can be made with up to 10 % weight fraction of polyaniline. Samples were observed with optical microscopy and calorimetry. With polyaniline-camphorsulphonate weight fractions below 10 %, melting point depression of the mixture was observed. On the other hand, pure polyaniline-camphorsulphonate does not melt. Hence the observations suggest eutectic phase behaviour, even though the actual eutectic point could not be reached due to the solubility limit. The aim was also to study the molecule complexes with small angle X-ray scattering. However, malfunction of the synchrotron beamline prevented from carrying out the intended measurements. The observed melting point depression indicates that polyaniline is dissolved in resorcinol at molecular level. This can have substantial conceptual significance as there have been claims that conjugated polymers cannot dissolve but remain as aggregates.Sähköä johtavia polymeerejä on tutkittu pyrittäessä uusiin pehmeän elektroniikan ja funktionaalisten materiaalien sovelluksiin. Johtavat polymeerit ovat kuitenkin jäykän ketjunsa vuoksi niukkaliukoisia, eivätkä ne yleensä sula. Tässä työssä tutkitaan polyaniliinin sulamispisteen alentamista resorsinolin avulla, mikä antaisi mahdollisuuden polyaniliinin prosessointiin sulatyöstön avulla. Työn tavoitteena on selvittää polyaniliinin ja resorsinolin seosten faasikäyttäytymistä ja tutkia polyaniliinin liukoisuutta resorsinoliin molekyylitasolla. Polyaniliinista ja resorsinolista valmistettiin seoksia eri massaosuuksilla. Havaittiin, että alle 10 % massaosuuksilla polyaniliinin kamferisulfonaattia voidaan sekoittaa resorsinoliin siten, että saadaan homogeeninen seos. Optisen mikroskopian ja kalorimetrian avulla havaittiin, että alle 10 % seoksen sulamispiste alenee puhtaaseen resorsinoliin verrattuna. Puhdas polyaniliinin kamferisulfonaatti ei sula, joten havainnot viittaavat eutektiseen faasikäyttäytymiseen. Eutektista pistettä ei tosin saavutettu; tiima johtunee alhaisesta liukoisuusrajasta. Molekyylikompleksien rakennetta pyrittiin tutkimaan röntgensäteilyllä synkrotronilahteen avulla. Laiterikon vuoksi näitä mittauksia ei voitu suorittaa loppuun. Työssä havaitusta sulamispisteen alenemasta päätellään, että molekyylitasolla polyaniliini on liuenneena sulaan resorsinoliin. Tällä voi olla huomattava periaatteellinen merkitys, sillä on esitetty väitteitä, että johdepolymeerit eivät voisi liueta liuottimiin, vaan ne muodostaisivat aina aggregaatteja

Itsejärjestyneiden nanomateriaalien rakennetutkimus

Controlling the self assembly of nanoparticles and block copolymers is an effective method to fine tune bulk structures in nanometer length scales. The small angle X-ray diffraction (SAXS) is the most reliable method to proof the existence of bulk morphology in nanometer length scales. In this study a custom-built instrument for measuring SAXS is designed and built by the author. The instrument is designed so that the angular resolution is comparable to small angle beamlines in the synchrotron facilities. All key functionalities are controlled from the computer. This allows programming automatic measurement series from tens of samples. Sample-to-detector distance can be adjusted from 0.5 meters up to 5 meters which allows high quality measurements of periodic structures from 1 nm beyond 300 nm. The author has used the SAXS instrument in Publications I – IV to reliably define the type of the bulk morphology of various self assembled systems. In addition, the instrument has been used in tens of other publications. In Publication I the self assembly of cowpea chlorotic mottle viruses and gold nanoparticles is demonstrated. They form an AB8fcc crystal structure that is not isostructural with any known atomic or molecular crystal structure and has previously been observed only with large colloidal polymer particles. It is shown that protein cage-guided formation of nanoparticle superlattices provides a biocompatible platform that allows the development of delivery applications and sensing applications in biological systems. In Publication II it is shown that recombinant ferritin protein cages encapsulating iron oxide and photodegradable Newkome-type dendrons self-assemble into micrometer-sized complexes with a face centered cubic superstructure. Self assembly of ABC triblock terpolymers show versatile morphologies. Certain morphologies can be used in synthesizing Janus nanoparticles. In Publication III the bulk phase behavior of polystyrene–block–polybutadiene–block–poly(tert–butyl methacrylate) triblock terpolymers is mapped. Different morphologies were identified including lamella, core-shell cylinder, cylinders in lamella interface and core-shell gyroid morphology. Versatile morphologies can be used as templates for further processing for various applications. In Publication IV the manipulation of polystyrene–block–poly(4–vinylpyridine)–block-poly(tert–butyl methacrylate) triblock terpolymer bulk morphologies through hydrogenbonding with rod-like 4–(4–pentylphenylazo)phenol is described and possibilities to fine tune the morphologies are demonstrated. Various bulk morphologies are characterized using SAXS including cylinders in lamella interface, multi layer ABCB-lamella and perforated lamella. Certain bulk morphologies can be used to produce Janus cylinders, Janus sheets and perforated Janus sheets. The perforated Janus sheets represent a "nanoporous membrane" with a pore diameter of about 20 nm and two different chemical structures on each side of the membrane. These perforated Janus sheets could be used in selective permeation applications.Nanomittakaavan rakenteita voidaan tehokkaasti hienosäätää nanopartikkeleiden ja lohkopolymeerien itsejärjestymisen avulla. Periodisten nanometrimittakaavan rakenteiden tutkimuksessa pienen kulman röntgendiffraktio on luotettavin mittausmenetelmä. Tässä työssä on suunniteltu ja rakennettu pienen kulman röntgendiffraktiolaitteisto, jonka kulmaresoluutio on verrattavissa pienen kulman synkrotronilinjoihin. Tärkeimpiä toimintoja ohjataan tietokoneella ja kymmenien näytteiden automaattinen mittaaminen on mahdollista. Detektorin etäisyys näytteestä on säädettävissä 0.5 ja 5 metrin välillä, mikä mahdollistaa periodisten rakenteiden mittaamisen 1 nm kokoluokasta yli 300 nm kokoluokkaan. Diffraktiolaitteistoa on käytetty julkaisuissa I - IV useiden morfologioiden luotettavaan määritykseen. Lisäksi laitteistoa on käytetty kymmenissä muissa julkaisuissa. Julkaisussa I lehmänpavun kloroosiläikkävirus ja kultananopartikkelit itsejärjestyivät AB8fcc-tyyppiseen kiderakenteeseen, jollaista ei ole aikaisemmin havaittu atomi- tai molekyylikokoluokassa. Vastaava rakenne on aikaisemmin havaittu ainoastaan suurilla kolloidisilla polymeeripartikkeleilla mikrometrikokoluokassa. Lisäksi osoitettiin, että proteiinikuoria voidaan käyttää periodisten nanorakenteiden tuottamiseen, mikä avaa mahdollisuuksia monien bioyhteensopivien sovellusten kehittämiseksi. Julkaisussa II osoitettiin rautaoksidipartikkeleita ympäröivien proteiinikuorien ja valolla pilkottavissa olevien Newkome-tyyppisten dendronien itsejärjestyvän mikrometrin kokoluokkaa oleviksi rakenteiksi. Rakenteiden sisäinen kidepakkaus noudattaa pintakeskeistä kuutiollista hilarakennetta. ABC-kolmilohkopolymeerien itsejärjestyminen tuottaa monipuolisia morfologioita. Tiettyjen morfologioiden pohjalta voidaan tuottaa Janus-nanopartikkeleita. Julkaisussa III polystyreeni–lohko–polybutadieni–lohko–poly(tert–butyyli metakrylaatti) kolmilohkopolymeerin faasidiagrammi kartoitettiin. Määriteltyjä morfologioita olivat mm. lamelli, putkimainen sylinterirakenne, gyroidirakenne. Havaitut morfologiat mahdollistavat monipuolisten rakenteiden räätälöimisen erilaisille sovelluksille. Julkaisussa IV tutkittiin polystyreeni–lohko–poly(4–vinyylipyridiini)–lohko–poly(tert–butyyli metakrylaatti) kolmilohkopolymeerin morfologioiden säätämistä vetysitoutuneella 4–(4–pentyylifenyyliatso)fenolilla. Työssä pienen kulman röntgendiffraktiolaitteistolla havaittiin uusia itsejärjestyneitä rakenteita. Näihin kuului mm. sylinterirakenne lamellirakenteen rajapinnassa, monikerros ABCB-lamellirakenne ja perforoitu lamellirakenne. Useista morfologioista voidaan tuottaa Janus-sylintereitä, Janus-levyjä ja perforoituja Janus-levyjä. Perforoitu Janus-levy on nanohuokoinen kalvo, jonka eri puolilla on erilainen kemiallinen rakenne ja jonka huokoskoko on 20 nm kokoluokkaa. Tällaisia perforoituja Janus-kalvoja voidaan käyttää valikoivan läpäisyn sovelluksissa.

Direct imaging of nanoscopic plastic deformation below bulk <i><i>T</i></i>_g and chain stretching in temperature-responsive block copolymer hydrogels by Cryo-TEM

This work describes the thermoresponsive transition in polystyrene-block-poly(N-isopropylacrylamide)-block-polystyrene (PS-block-PNIPAM-block-PS) triblock copolymer hydrogels, as observed by both direct and reciprocal space in-situ characterization. The hydrogel morphology was studied in both the dry and wet state, at temperatures below and beyond the coil−globule transition of PNIPAM, using vitrified ice cryo-transmission electron microscopy (cryo-TEM), in-situ freeze-drying technique, and small-angle X-ray scattering (SAXS). The selected PS-block-PNIPAM-block-PS triblock copolymers were intentionally designed in such a molecular architecture to self-assemble into spherical and bicontinuous morphology with the poly(N-isopropylacrylamide) forming the continuous matrix. The phase behavior in bulk was directly investigated by SAXS as a function of temperature, while free-standing polymer thin films of samples quenched from different temperatures, allowed observing by cryo-TEM the changes in hydrogel microstructure. Finally, sublimation of water via controlled freeze-drying in the TEM column allowed studying systems without the presence of vitrified water, which enables direct imaging of the densely connected physically cross-linked polymer network. By combining these techniques on samples exhibiting both spherical and gyroidal morphologies, it was demonstrated that (i) PNIPAM form physically connected networks in spherical structures and bicontinuous morphologies in the gyroidal phase, (ii) in PNIPAM chains strands are strongly stretched above the polymer coil-to-globule transition, and (iii) surprisingly, upon the gel swelling process, the PS domains undergo extensive plastic deformation although temperature is always maintained well below the PS glass transition bulk temperature. The possible physical mechanisms responsible for this plastic deformation can be understood in terms of the dependence of PS glass transition temperature on the size of nanometer-scaled domains

Double Gyroid Network Morphology in Supramolecular Diblock Copolymer Complexes

The double gyroid network morphology has been the focus of extensive research efforts as one of the most appealing block copolymer structures for practical applications. We performed an extensive study of the phase behavior of the supramolecular complex PS-b-P4VP(PDP)x to develop a systematic route to its double gyroid morphology. The morphological characterization of complexes was accomplished by transmission electron microscopy (TEM) and small-angle X-ray scattering (SAXS). Several compositions with the cubic Ia3¯d symmetry were found in a narrow region between the lamellar and the cylindrical phase. Experimental TEM images were compared to computer simulations of projections through multiple gyroid planes. Typical gyroid patterns—“double wave” and “wagon wheel”—were regularly found. The size of the gyroid unit cell was calculated from the SAXS data. The lattice parameter could be varied (from ca. 70 to 125 nm) by altering the molar mass of the block copolymer precursors. A number of complexes were found to exhibit characteristic biphasic morphologies—coexisting lamellar and gyroid phase or gyroid and cylindrical phase. Finally, gyroid complexes with different relative PDP ratios were obtained which provides the opportunity to generate nanoporous structures with tunable porosities by dissolving the amphiphiles.

Effect of temperature, water content and free fatty acid on reverse micelle formation of phospholipids in vegetable oil

The self-assembly of phospholipids in oil, specifically lecithin in rapeseed oil, was investigated by combining experimental and computational methods The influence of temperature, water, and free fatty acids on the onset of lecithin aggregation in the rapeseed oil was determined using the 7,7,8,8 -tetracyanoquinodimethane dye (TCNQ) solubilization method and the size and shape of the self-assembled lecithin structures were investigated by small-angle X-ray scattering and cryogenic transmission electron microscopy. In the absence of excess water in the system (0.03 wt-% water in oil), stable cylindrical lecithin reverse micelles were observed above the critical micelle concentration (CMC). Comparing the aggregation response in room temperature and at 70 °C revealed that CMC decreased with increasing temperature. Furthermore, already a modest amount of added water (0.3 wt-% water in oil) was sufficient to induce the formation of lamellar lecithin structures, that phase separated from the oil. In low water content, oleic acid suppressed the formation of lecithin reverse micelles whereas in the presence of more water, the oleic acid stabilized the reverse micelles. Consequently, more water was needed to induce phase separation in the presence of oleic acid. Molecular dynamics simulations indicated that the stabilizing effect of oleic acid resulted from oleic acid enhancing phospholipid solubilization in the oil by forming a solvating shell around the phosphate head group. The findings showed that the response of the mixed surfactant system is a delicate interplay of the different components and variables. The significance of the observations is that multiple parameters need to be controlled for desired system response, for example towards vegetable oil purification or phospholipid based microemulsions.Peer reviewe

Nanoporous Network Channels from Self-Assembled Triblock Copolymer Supramolecules

Supramolecular complexes of a poly(tert-butoxystyrene)-block-polystyrene-block-poly(4-vinylpyridine) triblock copolymers and less than stoichiometric amounts of pentadecylphenol (PDP) are shown to self-assemble into a core–shell gyroid morphology with the core channels formed by the hydrogen-bonded P4VP(PDP) complexes. After structure formation, PDP was removed using a simple washing procedure, resulting in well-ordered nanoporous films that were used as templates for nickel plating.