Synteettisiä ja Suprakolloidaalisia Konsepteja Selluloosan Nanokiteille

Modern technology requires sustainable solutions for future raw materials and applications. Nanocelluloses, namely cellulose nanocrystals (CNCs) and cellulose nanofibrils (CNF) are of particular interest as renewable, widely available, and highly functionalizable nano-sized raw materials. In this thesis, the fundamental properties of CNCs and their use in synthetic and colloidal self-assembly concepts for novel functional materials were explored. The proper utilization of CNCs for example in films, which reflect color for a selected wavelength, requires understanding of the basic properties for CNCs, both in dry and in liquid state. In publication I the chiral structure of dried CNC films was characterized with scanning electron microscopy (SEM). The method allows direct observation of the left-handed twisting sense and the optical period down to hundreds of nanometres for the self- assembled CNCs. In publication II a controlled polymerization procedure for well-defined polymer brushes tethered from the surface of CNCs was developed. Hydrophobic or hydrophilic brushes could be obtained with high grafting density. This modification route enabled further advanced targeted use for CNCs by exploiting supramolecular ionic complexation of the surface-grafted polyelectrolyte chains toward functionalities and applications.Dendron architecture combined with sugar molecule functionality offers a practical route for self-assembly using multivalent binding with moieties like nanoparticles, block copolymers or surfaces. In publication III strong interactions between maltose-based sugar-functionalized dendronized polymers (DenPols) and CNCs were recognized. The third generation DenPol wrapped around individual CNCs, as directly visualized by cryo high-resolution transmission electron microscopy and electron tomography. The considerable size of the DenPol allowed direct visualization of the wrapping phenomena with cryo-electron microscopy. In publication IV it was demonstrated both experimentally and theoretically, how a chiral plasmonic optical signal could be obtained through interaction between gold nanoparticles and chiral CNCs as dispersed in aqueous phase. This can create new possibilities, for example in sensing chiral molecules with the aid of chiral gold nanoparticle-CNC superstructures. This was the first time that the chiral right-handed twist along individual CNCs was used for a chiral plasmonic response. The results obtained in this thesis contribute to the fundamental understanding of the properties, behavior and manipulation of CNCs as a charged and chiral rod-like nanoparticle towards practical application, like self-healing hydrogels, glue additives, enantiomer separation, and potentially even security paper with structural color.Teknologiassa tarvitaan kestäviä ratkaisuja sovelluksilta ja niihin valituilta materiaaleilta. Selluloosan nanokiteet ja nanokuidut kiinnostavat uusiutuvina, laajalti saatavilla olevina ja hyvin muokattavina raaka-aineina. Tässä väitöskirjassa perehdyttiin selluloosan nanokiteiden perusominaisuuksiin sekä kiteiden synteettisesti muokattuihin ja itsejärjestäytyneisiin rakenteisiin tavoitellen uusia toiminnallisia materiaaleja. Nanokiteiden hyötykäyttö, esimerkiksi yhtä aallonpituutta heijastavissa värikkäissä kalvoissa edellyttää nanokiteiden perusominaisuuksien ymmärtämistä niin kiinteässä kuin nestetilassa. Julkaisussa I havaittiin pyyhkäisyelektronimikroskooppisin keinoin selluloosan nanokiteiden pakkautuminen kierteisesti kuivissa kalvoissa. Kalvoissa nanokiteet itsejärjestäytyvät vasenkätisesti. Optinen jaksollisuus määrittettiin alle mikrometrin tarkkuudella. Julkaisussa II kehitettiin kontrolloitu polymerointimenetelmä hyvin määriteltyjen polymeeriketjujen liittämiseen selluloosan nanokiteen pinnalle. Menetelmällä syntetisoidaan sekä vettä hylkiviä että suosivia polymeeriketjuja korkein oksastustiheyksin. Polymeerimuokatut nanokiteet mahdollistavat käyttökohteita esimerkiksi lujittajina komposiiteissa ja varauksen sitojana. Selluloosan nanokiteissä voidaan hyödyntää ionisia ja vetysidos vuorovaikutuksia. Julkaisussa III havaittiin maltoosi-sakkarideilla muokatun dendronoidun polymeerin voimakas vuorovaikutus selluloosan nanokiteen kanssa lukuisin vetysidoksin. Kietoutuminen visualisoitiin kryogeenisen elektronimikroskopian ja elektronitomografian avulla. Sokeriyksiköillä modifioidun haarautuneen molekyylin sitoutumista nanoselluloosaan voidaan hyödyntää muihin nanopartikkeleihin, lohkopolymeereihin ja pinnoille saavuttaen uusia ominaisuuksia itsejärjestäytyneille materiaaleille. Julkaisussa IV osoitettiin sekä kokeellisesti että teorian avulla, kuinka kytkemällä kultananohiukkasia selluloosan nanokiteeseen aikaansaadaan kiraalinen plasmoninen optinen signaali. Tämä luo uusia mahdollisuuksia esimerkiksi sensorointiin kiraalisten molekyylien tunnistamisessa hyödyntäen kultananohiukkasten ja nanokiteen itsejärjestäytymistä. Työssä hyödynnettiin ensimmäistä kertaa yksittäisen selluloosan nanokiteen oikeakätistä kierteisyyttä kiraalisen plasmonisen vasteen aikaansaamiseksi. Väitöskirjan tulokset edistävät ymmärrystä selluloosan nanokiteiden ominaisuuksista, käyttäytymisestä ja muokkaamisesta. Tuloksia voidaan hyödyntää sovelluksissa itsekorjautuville hydrogeeleille, liimaukseen, enantiomeerien erottelulle, mahdollisesti jopa turvallisuustietojen yhdistämiseen paperille

Unidirectional Perpendicularly Aligned Lamella-Structured Oligosaccharide (A) ABA Triblock Elastomer (B) Thin Films Utilizing Triazolium + /TFSI – Ionic Nanochannels

International audienc

Form-stable phase change materials from mesoporous balsa after selective removal of lignin

| openaire: EC/H2020/788489/EU//BioElCellWe produce balsa-based structures by selective removal of lignin. The changes that occur in the main components of balsa upon delignification, including tracheids, closed pits and tylosis vessels, allow the development of mesopores and a substantial increase in fluid permeability. Such system is ideally suited as a support of phase change materials, PCM. Vacuum-assisted impregnation with polyethylene glycol (PEG, a PCM), results in a form-stable PCM system (FPCM). The FPCM displays a high encapsulating capacity (83.5%) at temperatures above the melting PEG transition, with a latent heat of 134 J/g and low supercooling (12 °C). The results are rationalized by the affinity between the unidirectional mesoporous structure and the polymer, involving capillary forces and hydrogen bonding. The leakage-proof FPCM outperforms available systems (based on PEG or other PCMs) supported on minerals or other wood species. Compared to the latter group, the results obtained with balsa relate with its morphology and the effectof residual hemicelluloses in hierarchically-aligned cellulose nano- and microfibrils. The FPCMs resist compressive loads and performs stably for at least 200 cycles of heating and cooling. An insignificant loss in latent heat is observed compared to that of pure PEG. The phase transition temperature fluctuation and non-leaking characteristics under load make the balsa-based FPCM a superior alternative for passive heating/cooling, especially for uses at high ambient temperatures. The reversible thermoregulatory capacity, low cost, high efficiency, renewability, and operability of the balsa-supported FPCM, indicate an excellent option for thermal energy storage and conversion devices.Peer reviewe

Drying stresses in cellulose nanocrystal coatings: Impact of molecular and macromolecular additives

| openaire: EC/H2020/788489/EU//BioELCell Funding Information: We acknowledge funding support by the European Research Council under the advanced grant 788489 BioElCell. Luiz G. Greca & Karl Mihhels acknowledge funding from Aalto University School of Chemical Engineering and Konrad W. Klockars acknowledges funding from the Walter Ahlström Foundation . We acknowledge the support by Aalto University at OtaNano — Nanomicroscopy Center (Aalto-NMC). The authors are also grateful for the support of the Academy of Finland through its Centres of Excellence Programme (2014–2019) under Project 264677 “Molecular Engineering of Biosynthetic Hybrid Materials Research” (HYBER). We thank Prof. Olli Ikkala for his insightful comments. BLT is the recipient of the Khalifa University of Science and Technology (KUST) Faculty Startup Project (Project code: 84741140-FSU-2022-021 ). Publisher Copyright: © 2022The industrial implementation of cellulose nanocrystals (CNCs) in films and coatings requires thorough evaluation of the internal stresses post-consolidation, as they cause fracturing and peeling. Characterizing the impact of plasticizing additives on stress is therefore critical. Herein, we use the deflection of thin glass substrates to measure drying stresses in consolidating CNC films, and benchmark the impact of five additives (glucose, glycerol, poly(ethylene glycol) (PEG), poly(vinyl alcohol) (PVA) and bovine serum albumin). Glycerol and PEG reduced drying stresses effectively, while PEG of increased molecular weight (from 0.2 to 10 kDa), PVA, and BSA were less effective. We analyzed the temporal aspects of the process, where stress relaxation of up to 30 % was observed 2 years after coating formation. Finally, we provide a framework to evaluate the impact of CNC morphology on residual stresses. The introduced approach is expected to fast-track the optimization and implementation of coatings based on biocolloids.Peer reviewe

Deconstruction and Reassembly of Renewable Polymers and Biocolloids into Next Generation Structured Materials

| openaire: EC/H2020/788489/EU//BioELCellThis review considers the most recent developments in supramolecular and supraparticle structures obtained from natural, renewable biopolymers as well as their disassembly and reassembly into engineered materials. We introduce the main interactions that control bottom-up synthesis and top-down design at different length scales, highlighting the promise of natural biopolymers and associated building blocks. The latter have become main actors in the recent surge of the scientific and patent literature related to the subject. Such developments make prominent use of multicomponent and hierarchical polymeric assemblies and structures that contain polysaccharides (cellulose, chitin, and others), polyphenols (lignins, tannins), and proteins (soy, whey, silk, and other proteins). We offer a comprehensive discussion about the interactions that exist in their native architectures (including multicomponent and composite forms), the chemical modification of polysaccharides and their deconstruction into high axial aspect nanofibers and nanorods. We reflect on the availability and suitability of the latter types of building blocks to enable superstructures and colloidal associations. As far as processing, we describe the most relevant transitions, from the solution to the gel state and the routes that can be used to arrive to consolidated materials with prescribed properties. We highlight the implementation of supramolecular and superstructures in different technological fields that exploit the synergies exhibited by renewable polymers and biocolloids integrated in structured materials.Peer reviewe

Rod-Like Nanoparticles with Striped and Helical Topography

The behavior of nanoparticles in solution is largely dominated by their shape and interaction potential. Despite considerable progress in the preparation of patchy and compartmentalized particles, access to nanoparticles with complex surface patterns and topographies remains limited. Here, we show that polyanionic brushes tethered to rod-like cellulose nanocrystals (CNCs) spontaneously develop a striped or helical topography through interpolyelectrolyte complexation with polycationic diblock copolymers. Using cryogenic transmission electron microscopy (cryo-TEM) and tomography (cryo-ET), we follow the complexation process and analyze the delicate 3D topography on the CNC surface. The described approach is facile and modular and can be extended to other block chemistries, nanoparticles, and surfaces, thereby providing a versatile platform toward surface-patterned particles with complex topographies and spatially arranged functional groups

Chiral Plasmonics Using Twisting along Cellulose Nanocrystals as a Template for Gold Nanoparticles

The right-handed twist along aqueous dispersed cellulose nanocrystals allows right-handed chiral plasmonics upon electrostatic binding of gold nanoparticles in dilute environment, upon tuning the particle sizes and concentrations. Simulations using nanoparticle coordinates from cryo-electron tomography confirm the experimental results. The finding suggests generalization for other chiral and helical colloidal templates for nanoscale chiral plasmonics.Peer reviewe