TY - GEN A1 - Ermeydan, Mahmut Ali A1 - Cabane, Etienne A1 - Gierlinger, Notburga A1 - Koetz, Joachim A1 - Burgert, Ingo T1 - Improvement of wood material properties via in situ polymerization of styrene into tosylated cell walls N2 - As an engineering material derived from renewable resources, wood possesses excellent mechanical properties in view of its light weight but also has some disadvantages such as low dimensional stability upon moisture changes and low durability against biological attack. Polymerization of hydrophobic monomers in the cell wall is one of the potential approaches to improve the dimensional stability of wood. A major challenge is to insert hydrophobic monomers into the hydrophilic environment of the cell walls, without increasing the bulk density of the material due to lumen filling. Here, we report on an innovative and simple method to insert styrene monomers into tosylated cell walls (i.e. –OH groups from natural wood polymers are reacted with tosyl chloride) and carry out free radical polymerization under relatively mild conditions, generating low wood weight gains. In-depth SEM and confocal Raman microscopy analysis are applied to reveal the distribution of the polystyrene in the cell walls and the lumen. The embedding of polystyrene in wood results in reduced water uptake by the wood cell walls, a significant increase in dimensional stability, as well as slightly improved mechanical properties measured by nanoindentation. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 274 Y1 - 2014 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-98736 ER - TY - GEN A1 - Ermeydan, Mahmut Ali A1 - Cabane, Etienne A1 - Hass, Philipp A1 - Koetz, Joachim A1 - Burgert, Ingo T1 - Fully biodegradable modification of wood for improvement of dimensional stability and water absorption properties by poly(ε-caprolactone) grafting into the cell walls N2 - Materials derived from renewable resources are highly desirable in view of more sustainable manufacturing. Among the available natural materials, wood is one of the key candidates, because of its excellent mechanical properties. However, wood and wood-based materials in engineering applications suffer from various restraints, such as dimensional instability upon humidity changes. Several wood modification treatments increase water repellence, but the insertion of hydrophobic polymers can result in a composite material which cannot be considered as renewable anymore. In this study, we report on the grafting of the fully biodegradable poly(ε-caprolactone) (PCL) inside the wood cell walls by Sn(Oct)2 catalysed ring-opening polymerization (ROP). The presence of polyester chains within the wood cell wall structure is monitored by confocal Raman imaging and spectroscopy as well as scanning electron microscopy. Physical tests reveal that the modified wood is more hydrophobic due to the bulking of the cell wall structure with the polyester chains, which results in a novel fully biodegradable wood material with improved dimensional stability. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 270 KW - ring-opening polymerization KW - confocal raman microscopy KW - epsilon-caprolactone KW - mechanical-properties KW - structural-characterization KW - stannous octoate KW - copolymers KW - degradation KW - composites KW - cellulose Y1 - 2014 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-97265 SP - 3313 EP - 3321 ER - TY - THES A1 - Ermeydan, Mahmut Ali T1 - Wood cell wall modification with hydrophobic molecules T1 - Modifikation von Holzzellwänden durch hydrophobe Moleküle N2 - Wood is used for many applications because of its excellent mechanical properties, relative abundance and as it is a renewable resource. However, its wider utilization as an engineering material is limited because it swells and shrinks upon moisture changes and is susceptible to degradation by microorganisms and/or insects. Chemical modifications of wood have been shown to improve dimensional stability, water repellence and/or durability, thus increasing potential service-life of wood materials. However current treatments are limited because it is difficult to introduce and fix such modifications deep inside the tissue and cell wall. Within the scope of this thesis, novel chemical modification methods of wood cell walls were developed to improve both dimensional stability and water repellence of wood material. These methods were partly inspired by the heartwood formation in living trees, a process, that for some species results in an insertion of hydrophobic chemical substances into the cell walls of already dead wood cells, In the first part of this thesis a chemistry to modify wood cell walls was used, which was inspired by the natural process of heartwood formation. Commercially available hydrophobic flavonoid molecules were effectively inserted in the cell walls of spruce, a softwood species with low natural durability, after a tosylation treatment to obtain “artificial heartwood”. Flavonoid inserted cell walls show a reduced moisture absorption, resulting in better dimensional stability, water repellency and increased hardness. This approach was quite different compared to established modifications which mainly address hydroxyl groups of cell wall polymers with hydrophilic substances. In the second part of the work in-situ styrene polymerization inside the tosylated cell walls was studied. It is known that there is a weak adhesion between hydrophobic polymers and hydrophilic cell wall components. The hydrophobic styrene monomers were inserted into the tosylated wood cell walls for further polymerization to form polystyrene in the cell walls, which increased the dimensional stability of the bulk wood material and reduced water uptake of the cell walls considerably when compared to controls. In the third part of the work, grafting of another hydrophobic and also biodegradable polymer, poly(ɛ-caprolactone) in the wood cell walls by ring opening polymerization of ɛ-caprolactone was studied at mild temperatures. Results indicated that polycaprolactone attached into the cell walls, caused permanent swelling of the cell walls up to 5%. Dimensional stability of the bulk wood material increased 40% and water absorption reduced more than 35%. A fully biodegradable and hydrophobized wood material was obtained with this method which reduces disposal problem of the modified wood materials and has improved properties to extend the material’s service-life. Starting from a bio-inspired approach which showed great promise as an alternative to standard cell wall modifications we showed the possibility of inserting hydrophobic molecules in the cell walls and supported this fact with in-situ styrene and ɛ-caprolactone polymerization into the cell walls. It was shown in this thesis that despite the extensive knowledge and long history of using wood as a material there is still room for novel chemical modifications which could have a high impact on improving wood properties. N2 - Der nachwachsende Rohstoff Holz wird aufgrund seiner guten mechanischen Eigenschaften und der leichten Verfügbarkeit für viele Anwendungszwecke genutzt. Quellen und Schrumpfen bei Feuchtigkeitsänderungen des hygroskopischen Werkstoffs Holz limitieren jedoch die Einsatzmöglichkeiten. Ein weiteres Problem stellt der mitunter leichte Abbau – u.a. bei feuchtem Holz - durch Mikroorganismen und/oder Insekten dar. Durch chemische Modifizierungen können die Dimensionsstabilität, die Hydrophobizität und die Dauerhaftigkeit verbessert und damit die potentielle Lebensdauer des Werkstoffes erhöht werden. Dabei ist die dauerhafte Modifikation der Zellwand nur äußerst schwer realisierbar. Inspiriert von der Kernholzbildung in lebenden Bäumen, ein zellwandverändernder Prozess, der Jahre nach der Holzbildung erfolgt, wurden im Rahmen dieser Arbeit neue Ansätze zur chemischen Modifizierung der Zellwände entwickelt, um die Dimensionsstabilität und Hydrophobizität zu erhöhen. Der erste Teil der Arbeit ist stark vom Prozess der Kernholzbildung inspiriert, eine abgeleitete Chemie wurde verwendet, um die Zellwände von Fichte, einem Nadelholz von geringer natürlicher Dauerhaftigkeit, zu modifizieren. Kommerziell verfügbare hydrophobe Flavonoide wurden nach einem Tosylierungsschritt erfolgreich in die Zellwand eingebracht, um so „artifizielles Kernholz“ zu erzeugen. Die modifizierten Holzproben zeigten eine verringerte Wasseraufnahme, die zu erhöhter Dimensionsstabilität und Härte führte. Dieser Ansatz unterscheidet sich grundlegend von bereits etablierten Modifikationen, die hauptsächlich hypdrophile Substanzen an die Hydroxylgruppen der Zellwand anlagern. Der zweite Teil der Arbeit beschäftigt sich mit der Polymerisation von Styren in tosylierten Zellwänden. Es ist bekannt, dass es nur eine schwache Adhäsion zwischen den hydrophoben Polymeren und den hydrophilen Zellwandkomponenten gibt. Die hydrophoben Styren-Monomere wurden in die tosylierte Zellwand eingebracht und zu Polystyren polymerisiert. Wie bei der Modifikation mit Flavonoiden konnte eine erhöhte Dimensionsstabilität und reduzierte Wasseraufnahme der Zellwände beobachtet werden. Im dritten Teil der Arbeit wurde das biologisch abbaubare, hydrophobe poly(ɛ-caprolacton) in der Zellwand aufpolymerisiert. Die Ergebnisse deuten darauf hin, dass Polycaprolacton in der Zellwand gebunden ist und zu einer permanenten Quellung führt (bis zu 5 %). Die Dimensionsstabilität nahm um 40 % zu und die Wasseraufnahmerate konnte um mehr als 35 % reduziert werden. Mit dieser Methode kann nicht nur dimensionsstabileres Holz realisiert werden, auch biologische Abbaubarkeit und damit eine einfache Entsorgung sind gewährleistest. KW - Holzmodifikation KW - hydrophobe Moleküle KW - Dimensionsstabilität KW - Wassergehalt KW - wood modification KW - hydrophobic molecules KW - dimensional stability KW - moisture content Y1 - 2014 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-71325 ER -