Local heterogeneities can have significant effects on the performance of anti-corrosion coatings. Even small features can act as initiation points for damage and result in corrosion of the substrate material. Analysis methods with high spatial resolution and the ability to collect information relevant to crosslinking and degradation behavior of these coatings are therefore highly relevant. In this work, we demonstrate the utility of nanomechanical AFM measurements and nano-FTIR in investigating the nanoscale mechanical and chemical properties of two polyester coil coating clearcoats before and after weathering. On the nanoscale, weathering led to a stiffer and less deformable coating with less variation in the nanomechanical properties. Chemical degradation was quantified using changes in band ratios in the IR-spectra. Macro and nano-scale measurements showed similar trends with the latter measurements showing larger heterogeneity. Our results demonstrate the usefulness of the described analysis techniques and will pave the way for future studies of local properties in other coating systems and formulations.

Poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) is currently used for a wide range of applications, often involving the synthesis of block copolymers. Here, an in-depth characterization of PDMAEMA prepared by atom transfer radical polymerization (ATRP) is reported, with a focus on end group analysis. The structure of the polymer was elucidated by one- and two-dimensional NMR spectroscopy, which assessed the presence of deactivated chains and allowed for a quantification of their fraction. Detailed characterization by MALDI-TOF MS further provided insightful information about the chain end fidelity. On this basis, termination by disproportionation was found to be the main mechanism for the loss of active chain ends. The detailed characterization allowed for an estimation of the preserved chain end functionality (CEF) of PDMAEMA. Additionally, a chain extension experiment was conducted, using PDMAEMA as a macroinitiator for the polymerization of methyl methacrylate (MMA) by ATRP. The results of chain extension supported the estimation of CEF based on the data provided by NMR and MS. Although assessing the degree of polymerization of a block copolymer proves challenging when the amount of the initial block able to act as a macroinitiator is not known a priori, an accurate estimation of the DP and M-n of the obtained block copolymer was possible by total nitrogen analysis. The tools here provided for the characterization of PDMAEMA and its block copolymer architectures allow the obtainment of essential information about the extent of control over the homo- and copolymerization. Therefore, they are of high importance when well-defined structures are aimed for.

In light of the need to redesign industrially produced materials by utilizing renewable resources, nanoscopic forms of cellulose are regarded as a valuable asset. In this work, the potential of cellulose nanofibrils (CNFs) as an unconventional nanoadditive for a polyester-melamine coil coating formulation is explored. CNFs, hydrophilic nanomaterials with high aspect ratios, were successfully incorporated in the solvent-borne formulation. Coatings were prepared with extremely low loadings of the nanoadditive (0.5 and 0.7 wt%). At these concentrations, the volume fraction of the nanofibrils in the coatings was calculated to be close to their percolation threshold. Two different pathways of CNF surface modification were applied to allow for a good compatibilization in the resin matrix, and the formulations were cured in two different settings. The effective compatibilization of the nano -additive led to a significant variation of the viscoelastic properties in the coatings containing CNFs. The results from dynamic mechanical analysis (DMA) highlighted the effect of CNFs on the crosslinked network at the nanoscale, resulting in an increase in Tg. Additionally, an increase in the stress at break and Young's modulus was determined by tensile testing, while satisfactory elongation at break was preserved. Other relevant effects induced by the presence of CNFs on the properties of the coatings were highlighted, such as a significant matt effect, increased surface roughness and lower scratch resistance. A preliminary evaluation of the water barrier properties by electrochemical impedance spectroscopy (EIS) is also presented, suggesting that the incorporation of a hydrophilic nanoadditive did not lead to a deterioration of the coatings' performance.

Magnifying the nanostructure of wood reveals the features of an extraordinary nanocomposite material. In this nanocomposite, long fibrils of semicrystalline cellulose, with a cross-section in the nanometer range and length up to several micrometers, are embedded in an amorphous matrix made of other polymeric components. Cellulose is the load-bearing skeleton responsible for the mechanical strength of plant tissues, while the matrix cements the fibrils together and provides flexibility. 

Ever since the first methods were developed for producing individualized cellulose nanofibrils (CNFs), materials scientists have explored the potential of these biobased nanomaterials as reinforcement for nanocomposite applications. In light of the quest for renewable alternatives to fossil-based materials, both for common use and high-value applications, wood nanocomponents offer important opportunities. However, dispersing CNFs within conventional polymer matrices entails challenges related to the hydrophilic–hydrophobic character of the nanofibril–matrix interface. In this context, the aim of this thesis is to evaluate strategies for compatibilizing CNFs in relatively hydrophobic polymer matrices. 

Three different nanocomposite applications were explored by incorporating low loadings of CNFs (0.5–6 wt%) in polymer matrices. The properties of the nanofibril–matrix interface were modified by two alternative approaches, both based on the adsorption of copolymers onto CNFs in water dispersion. In the first part of the work, a tailor-made random copolymer was adsorbed onto the CNF surface and used as a macroinitiator for the in situ polymerization of methacrylate monomers by aqueous atom transfer radical polymerization (ATRP). The second part focuses on the adsorption onto CNFs of amphiphilic block copolymers synthesized by ATRP to function as CNF–matrix compatibilizers. Synthetic and analytical aspects related to the design of well-defined structures were investigated, as well as fundamental parameters affecting their adsorption onto cellulose. The use of amphiphilic block copolymers as CNF–matrix compatibilizers was explored both while targeting the dispersion of CNFs in a thermosetting coating resin, and in a thermoplastic polymer matrix. 

The outcomes of this work highlight significant effects induced by surface-modified CNFs on the structural and mechanical properties of the studied nanocomposite materials.

Om man tittar på trä med hög förstoring framkommer ett extraordinärt nanokompositmaterial med långa fibriller av semikristallin cellulosa, med ett nanometerstort tvärsnitt och en längd på upp till flera mikrometer, inbäddade i en amorf matris av andra polymera komponenter. Cellulosa är det bärande skelettet och ansvarar för växters mekaniska styrka, medan matrisen binder ihop fibrillerna och förser strukturen med stabilitet. Ända sedan utvecklingen av de första metoderna för att producera enskilda cellulosananofibriller (CNF) har potentialen hos dessa biobaserade nanomaterial studerats som bärande material inom nanokomposittillämpningar. I sökandet efter förnybara alternativ till fossilbaserade material, för såväl vardaglig som högteknologisk användning, erbjuder de nanokomponenter som kan utvinnas ur trä många möjligheter. Men en utmaning vid användningen av CNF i konventionella polymermatriser är den hydrofila–hydrofoba karaktären i gränssnittet mellan nanofibriller och matris. Det är den utmaning som denna avhandling har haft som syfte att utforska genom att utvärdera strategier för att inkorporera CNF i relativt hydrofoba polymermatriser. Tre olika typer av nanokomposittillämpningar undersöktes, genom att inkorporera låga halter av CNF (0.5–6 wt%) i polymermatriser. Förhållandena i gränssnittet mellan nanofibriller och matris modifierades utifrån två olika tillvägagångssätt, båda baserade på adsorption av sampolymerer på CNF:er i vattenlösning. I den första delen av arbetet studerades adsorption av en skräddarsydd slumpmässig sampolymer på CNF‑ytan som sedan användes som makroinitiator för in situ-polymerisering av metakrylatmonomerer genom vattenbaserad kontrollerad radikalpolymerisation. I den andra delen studerades adsorption på CNF:er genom att använda amfifila blocksampolymerer som CNF-matrixkompatibilisatorer. Själva polymersyntesen och de analysmetoder som används vid karakterisering av väldefinerade polymerstrukturer utvärderades, liksom de grundläggande parametrar som påverkar deras adsorption på cellulosa. Användningen av amfifila blocksampolymerer som CNF-matrixkompatibilisatorer undersöktes för CNF inom värmehärdande ytbeläggningsapplikationer och som bärande material i en termoplastisk polymermatris. Arbetets resultat belyser hur modifierade CNF:er har betydande effekter på de studerade nanokompositmaterialens strukturella och mekaniska egenskaper.

Cellulose nanofibril (CNF)-networks are modified by the addition of small amounts (below 10 wt%) of well-defined cationic nanolatexes synthesized through reversible addition–fragmentation chain-transfer-mediated polymerization-induced self-assembly (PISA). Minute amounts of nanolatex inclusions lead to increased tensile and shear moduli, indicating that nanolatexes can act as bridging-points between CNFs. At higher nanolatex content, this stiffening effect is lost, likely due to interactions between nanolatexes leading to plasticization. The influence of nanolatex content and size on interparticle distance is discussed and is used as a tool to understand the effects observed in macroscopic properties. Upon annealing, the stiffening effect is lost due to the softening of the nanolatexes, indicating that the core–shell morphology is a prerequisite for this effect. These systems form a versatile platform to develop fundamental insights into complex condensed colloidal systems, to ultimately aid in the development of new sustainable material concepts.

An all-water-based procedure for "controlled" polymer grafting from cellulose nanofibrils is reported. Polymers and copolymers of poly(ethylene glycol) methyl ether methacrylate (POEGMA) and poly(methyl methacrylate) (PMMA) were synthesized by surface-initiated activators regenerated by electron transfer atom transfer radical polymerization (SI-ARGET ATRP) from the cellulose nanofibril (CNF) surface in water. A macroinitiator was electrostatically immobilized to the CNF surface, and its amphiphilic nature enabled polymerizations of both hydrophobic and hydrophilic monomers in water. The electrostatic interactions between the macroinitiator and the CNF surface were studied by quartz crystal microbalance with dissipation energy (QCM-D) and showed the formation of a rigid adsorbed layer, which did not desorb upon washing, corroborating the anticipated electrostatic interactions. Polymerizations were conducted from dispersed modified CNFs as well as from preformed modified CNF aerogels soaked in water. The polymerizations yielded matrix-free composite materials with a CNF content of approximately 1-2 and 3-6 wt % for dispersion-initiated and aerogel-initiated CNFs, respectively.