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The utilization and modification of cellulose, in particular nanocelluloses, for applications in bioplastics and biocomposites has been well studied in recent years. There is an increasing need for materials with good mechanical properties from renewable resources to replace current polymeric materials derived from fossil fuels. The modification of cellulose is essential to improve compatibility with hydrophobic matrices. For this purpose, various modification techniques have been employed such as physical adsorption of polymers to cellulosic substrates. This review aims to summarize the existing literature describing the physical adsorption of tailor-made copolymers to cellulosic surfaces. This area of cellulose modification incorporates a broad range of polymeric materials, and the expansion of this method of cellulose modification is promising for future sustainable, renewable and ‘green’ material development. [ABSTRACT FROM AUTHOR]

Abstract: The ability to reproduce a specified head-on-trunk position can be an indirect test of cervical proprioception. This ability is affected in subjects with neck pain, but it is unclear whether and how much pain or continuous muscle contraction factors contribute to this effect. We studied the influence of a static unilateral neck muscle contraction task (5 min of lateral flexion at 30% of maximal voluntary contraction) on head repositioning ability in 20 subjects (10 women, 10 men; mean age 37 years) with healthy necks. Head repositioning ability was tested in the horizontal plane with 30° target and neutral head position tests; head position was recorded by Zebris®, an ultrasound-based motion analyser. Head repositioning ability was analysed for accuracy (mean of signed differences between introduced and reproduced positions) and precision (standard deviation of the differences). Accuracy of head repositioning ability increased significantly after the muscle contraction task, as the normal overshoot was reduced. An average overshoot of 7.1° decreased to 4.6° after the muscle contraction task for the 30° target and from 2.2° to 1.4° for neutral head position. The increased accuracy was most pronounced for movements directed towards the activated side. Hence, prolonged unilateral neck muscle contraction may increase the sensitivity of cervical proprioceptors. [Copyright &y& Elsevier]

In the present work, poly(vinyl acetate) grafted cellulose nanocrystals (CNC- g -PVAc) were prepared via surface initiated reversible addition-fragmentation chain transfer and macromolecular design via the interchange of xanthates (SI-RAFT/MADIX) polymerization. Successful grafting of PVAc from CNC was confirmed by FT-IR and TGA analysis. PVAc nanocomposites reinforced with CNC- g -PVAc, as well as pristine CNC for comparison, of different weight percentages (0.5, 1, 3 and 5 wt%) of CNC were prepared via solvent casting. The PVAc reinforced with CNC- g -PVAc resulted in higher transparency and improved mechanical properties compared with unmodified CNC nanocomposites. The addition of 5 wt% CNC-g-PVAc increased the modulus of neat PVAc with as much as 154%. The proposed SI-RAFT/MADIX on CNC could be applied to wide range of monomers, and it is believed to be an efficient and robust method for CNC functionalization, thus expanding the potential applicability of CNC. [ABSTRACT FROM AUTHOR]

We investigated test to retest reliability and intraindividual variability of Romberg ratios in quiet stance posturography. Thirty-six healthy young adults (17 males, 19 females aged 15–38 years) were divided into 3 groups with different time-intervals between consecutive trials (20 min, 3 h and 24 h respectively). Each group performed 5 posturography recordings in a randomized order of eyes open (EO) or closed (EC) + once after 3 months. We measured the torque variance in posturography and calculated Romberg ratios. Total postural sway as well as sway above and below 0.1 Hz was analyzed. Results Test to retest reliability was found to be poor for Romberg ratios (intraclass correlation coefficients (ICC) <0.4) despite that the individual EO and EC posturography recordings were consistent. For sway >0.1 Hz the Romberg ratios were found to be more consistent (fair to good, ICC 0.49–0.71). The variation between two consecutive tests (absolute difference (%)) was high when using the traditional Romberg ratio (EC/EO), but became less varied if an alternate formula that includes the total postural sway was used ((EC − EO)/(EC + EO) × 100). Conclusion In healthy young adults the evaluation of ratios from repeated quiet stance posturography show great intraindividual inconsistency. This questions the Romberg ratio as being a reliable tool for evaluation of postural performance and determination of sensory preference in postural control, at least in healthy controls. Whether test–retest reliability is acceptable in patient cohorts needs to be evaluated for proper validity of intervention and outcome studies and for detection of clinical relevance. [ABSTRACT FROM AUTHOR]

In this work, a series of functional nanocrystals (F-CNCs) was successfully produced by an efficient preparation method, combining acid hydrolysis and Fischer esterification with various organic acids. Functionalities such as ATRP initiators, double bonds, triple bonds, and thiols could be incorporated on CNCs. Surface modification was confirmed by FT-IR, XPS, and elemental analysis. Physical properties of F-CNCs were assessed by AFM, XRD and TGA. Moreover, ATRP initiator functionalized CNCs were utilized to graft poly(methyl methacrylate) via ATRP, thiol functionalized CNCs were reacted with Ellman's reagent to determine the thiol content and dye disperse red 13 was attached to alkyne functionalized CNCs to estimate the propiolate content. The herein presented method is a highly versatile and straightforward procedure for the preparation of F-CNCs which is believed to be a better alternative for the commonly utilized, extensive, multistep, and time consuming post functionalization methods. [ABSTRACT FROM AUTHOR]

Poly(vinyl acetate), PVAc, adhesives are commonly used for wood bonding; however, they are fossil-based and the final products usually do not have a sufficient water resistance for more durable applications. In this study we prepared an adhesive formulation by grafting VAc from chitosan using emulsion polymerization, chitosan- graft -PVAc. Thereby, we could decrease the fossil-based content of the adhesive and at the same time significantly improve the water resistance. Chitosan by itself has very good bonding properties as a wood adhesive, especially regarding water resistance; however, very low solid contents of the adhesive formulation can be achieved due to a very high viscosity of chitosan adhesives. In our chitosan- graft -PVAc adhesives, we explored two chitosan samples with different molecular weights, by using as-received chitosan and hydrolyzing it to a lower molecular weight. The chitosan fractions in the adhesives prepared with a higher molecular weight chitosan were 15, 20 and 25 wt%. However, due to the high viscosity, a solid content higher than 17 wt% could not be achieved for these adhesives. Sufficient bond strengths were achieved when the adhesive was applied in 122 g/m2 solid spread rate. In order to decrease the viscosity, we used hydrolyzed chitosan, with a lower molecular weight, to allow for a higher adhesive solid content, 34 wt%, and for a higher chitosan fraction, 40 wt%. In the adhesive with 40 wt% chitosan and 17 wt% solid content, all VAc was grafted from chitosan. This decreased the molecular mobility of the chains, leading to a lower susceptibility to plastic creep in the adhesive which contributes to the final bond strength. The dry and wet strengths of the specimens bonded with adhesives containing chitosan were higher than the strength of the specimens bonded with the reference PVAc adhesive. [Display omitted] • Wood adhesives are prepared by grafting vinyl acetate from chitosan. • By the introduction of chitosan, the fossil content can be reduced by 40 %. • The water resistance of the PVAc adhesive is improved when chitosan is introduced. • A lower molecular weight chitosan allows for higher chitosan- and solid content. [ABSTRACT FROM AUTHOR]

Abstract: Functionalization of thermally expandable microspheres (TEMs) with a conjugated polymer is explored. These functionalized thermally expandable microspheres were prepared by grafting 3-n-dodecylthiophene via oxidative polymerization from a thiophene modified TEM. The thiophene modified TEM to 3-n-dodecylthiophene ratio was varied during grafting and the resulting poly(3-n-dodecylthiophene) grafted TEM were characterized by FT-IR spectroscopy, Thermal Gravimetric Analysis, Scanning Electron Microscopy, Thermo-Mechanical Analysis and X-ray diffraction. The particles were approximately 30μm in diameter and upon heating, the functionalized microspheres expanded up to 50 times. This expansion property was related to the poly(3-n-dodecylthiophene) content, where the increase in poly(3-n-dodecylthiophene) on microsphere decreased the thermal expansion. The X-ray diffraction shows a sharpening of the poly(3-n-dodecylthiophene) (100) diffraction peak upon expansion. Grafting conjugated polymers to thermally expandable microspheres provides robust functional photo- and electro-active TEMs. [Copyright &y& Elsevier]

Abstract: In this review, homogeneous and heterogeneous grafting from cellulose and cellulose derivatives by ring-opening polymerisation (ROP) are reported. Cellulose is biorenewable and biodegradable as well as a stiff material with a relatively low specific weight, foreseen to be an excellent replacement for synthetic materials. By utilising ROP of monomers such as ε-caprolactone or l-lactide from cellulose, composite materials with new and/or improved properties can be obtained. Grafting of solid cellulose substrates, such as cotton, microfibrillated cellulose (MFC) or cellulose nanocrystals, renders cellulose that can easily be dispersed into polymer matrices and may be used as reinforcing elements to improve mechanical and/or barrier properties of biocomposites. A surface grafted polymer can also tailor the interfacial properties between a matrix and the fibrillar structure of cellulose. When derivatives of cellulose are grafted with polymers in homogenous media, amphiphilic materials with interesting properties can be achieved, anticipated to be utilised for applications such as encapsulation and release. [Copyright &y& Elsevier]

Abstract: Wheat gluten, among other plant proteins, constitutes an attractive raw material for sustainable alternatives to today''s petroleum-based wood adhesives. Nevertheless, the bonding performance, and especially the water resistance, of these plant proteins need to be improved to turn them into competitors equal in merit to today''s petroleum-based products. The aim of this study was to investigate if mild hydrolysis or heat treatment of wheat gluten will improve its adhesive properties. Wheat gluten was hydrolyzed with the enzyme Alcalase (degree of hydrolysis 0.3–5.5%), or heat treated at different temperatures (50, 70, and 90°C) and varying time intervals (15min to 24h). Alkaline water dispersions of these modified wheat gluten samples were used as adhesives to bond together wood substrates of beech at a press temperature of 110°C and a press time of 15min. The tensile shear strengths of the substrates were measured for comparison of bond strength and resistance to cold water. The substrates were evaluated according to a slightly modified version of the European Standard EN 204. Lower levels of hydrolysis (0.3–0.6%) and most of the heat treatments at 90°C resulted in improved bond strength and water resistance. Nevertheless, the adhesive properties, especially the water resistance, need to be further improved to fulfill today''s requirements for wood adhesives. [Copyright &y& Elsevier]

Abstract: The tensile strength of beech substrates bonded with dispersions of alkali-denatured soy protein isolate (SPI) and wheat gluten (WG) was measured for comparison of bond strength and resistance to cold water. The proteins were denatured with 0.1M NaOH (pH 13). Dispersions with different protein concentration and viscosity were investigated. The adhesive properties were studied at different press temperatures (90, 110, and 130°C) and press times (5, 15, and 25min). Two types of application methods were used in order to overcome the problem with different viscosity of the dispersions. In addition, SPI was denatured at two different pH levels (approximately 10 and 13) and with two different concentrations of salt (158μM and 0.1M), in order to compensate for the different isoelectric points of the proteins. The adhesive properties of WG powder with different particle sizes were also compared. The tensile strengths of the wood substrates were measured according to somewhat simplified versions of the European Standards EN 204 and EN 205. The bond lines were studied with light microscopy. The results indicate that the adhesive properties of SPI are superior, particularly with regard to water resistance. However, the water resistance of WG was to some extent improved when starved adhesive joints could be avoided. Similar tensile strength values were obtained for the dispersions of alkali-denatured SPI regardless of pH or salt concentration. No apparent difference in adhesive strength was observed for the WG dispersions from powder with different particle sizes. [Copyright &y& Elsevier]

Abstract: Acrylonitrile (AN)-methacrylonitrile (MAN) copolymer particles with a core/shell structure were prepared by suspension polymerization. The particles were about 10–20μm in diameter and had a hollow core containing an inert hydrocarbon. The influence of the monomer feed ratio and the polymerization temperature on the particle morphology was studied. One purpose of this study was to determine the boundaries for achieving a core/shell structure with the polymer encapsulating the hydrocarbon. When polymerizing at 62°C, it was found that an initial AN/MAN feed ratio (f AN) between 0.15 and 0.9 results in core/shell particles with encapsulated hydrocarbon. f AN lower than 0.15 yielded solid particles with no hydrocarbon encapsulated while f AN higher than 0.9 yielded particles built up entirely from agglomerates of smaller primary particles. In contrast, when polymerizing at 80°C, a much narrower span of f AN (0.5–0.85) yielded particles with hydrocarbon encapsulated. The influence on monomer conversion and the molecular weight of the polymer was also studied. [Copyright &y& Elsevier]

The performance of different esterification catalysts was studied for the use in synthesis of renewable polyesters from dimethyl itaconate (DMI), dimethyl succinate (DMS) and 1,4-butanediol (BD). Itaconic acid and derivatives such as DMI are interesting monomers because of their multiple functionalities and previous work has shown great potential. However, the multiple functionalities also pose challenges to avoid side reactions such as thermally initiated, premature, radical crosslinking and/or isomerization of the 1,1-disubstituted unsaturation. Additionally, the two carboxylic acids have inherently different reactivity. One key factor to control reactions with IA is to understand the performance of different catalysts. In this study, six esterification catalysts were investigated; immobilized Candida antarctica lipase B (CalB), titanium(IV)butoxide (Ti(OBu) 4 ), p -toluenesulfonic acid ( p TSA), sulfuric acid (H 2 SO 4 ), 1,8-diazabicycloundec-7-ene (DBU), and 1,5,7-triazabicyclodec-5-ene (TBD). CalB and Ti(OBu) 4 were selected for further characterization with appreciable differences in catalytic activity and selectivity towards DMI. CalB was the most effective catalysts and was applied at 60 °C while Ti(OBu) 4 required 160 °C for a reasonable reaction rate. CalB was selective towards DMS and the non-conjugated side of DMI, resulting in polyesters with itaconate-residues mainly located at the chain ends, while Ti(OBu) 4 showed low selectivity, resulting in polyesters with more randomly incorporated itaconate units. Thermal analysis of the polyesters showed that the CalB-catalyzed polyesters were semi-crystalline, whereas the Ti(OBu) 4 -catalyzed polyesters were amorphous, affirming the difference in monomer sequence. The polyester resins were crosslinked by UV-initiated free radical polymerization and the material properties were evaluated and showed that the crosslinked materials had similar material properties. The films from the polyester resins catalyzed by CalB were furthermore completely free from discoloration whereas the film made from the polyester resins catalyzed with Ti(OBu) 4 had a yellow color, caused by the catalyst. Thus, it has been shown that CalB can be used to attain sustainable unsaturated polyesters resins for coating applications, exhibiting equally good properties as resins obtained from traditional metal-catalysis. [ABSTRACT FROM AUTHOR]

EDC-mediated coupling has frequently been utilized to poly(ethylene glycol) functionalize (PEGylate) cellulose-based materials, but no work has previously been reported on the direct N -(3-dimethylaminopropyl)- N -ethylcarbodiimide (EDC)-mediated PEGylation of cellulose nanofibrils (CNF). Herein, we report the first study where CNF has been directly sterically stabilized with amine-terminated PEG employing N -hydroxysuccinimide (NHS)-assisted EDC-coupling. This work has shown that this coupling reaction is highly sensitive to the reaction conditions and purification procedures, and hence an optimized coupling protocol was developed in order to achieve a reaction yield. Elemental analysis of the nitrogen content also showed the successful PEGylation. It was also shown that a surprisingly low PEGylation (1%) is sufficient to significantly improve the colloidal stability of the PEGylated samples, which reached dispersion-arrested-state-transitions at higher concentrations than neat CNF. The colloidal stability was preserved with increasing ionic strength, when comparably long polymer chains were grafted, targeting only 1% PEGylation. [ABSTRACT FROM AUTHOR]

Wood adhesives are mainly prepared from polymers derived from petroleum-based resources. With the increasing concern for the environment, it is necessary to find alternatives derived from bio-based resources that can replace petroleum-based polymers. To enable this transition it is important that the adhesive properties in terms of bond strength, water resistance and heat resistance are similar, and that the alternative can compete in terms of cost. Hemicelluloses are a byproduct from the pulp industry. From environmental and economic perspectives it is preferable to utilize all components from wood and decrease the amount of low-value byproducts. In this study, hemicelluloses are suggested to be used as binders in wood adhesives, why water dispersions of xylan have been prepared and evaluated. However, xylan itself cannot be used as a wood adhesive due to its limited bonding performance, especially regarding the water resistance. With the addition of dispersing agents, poly(vinyl alcohol) or poly(vinyl amine), and crosslinkers, such as glyoxal or hexa(methoxymethyl) melamine, the xylan dispersions demonstrate promising results. Wood veneers bonded with xylan dispersions and evaluated with ABES, Automated Bonding Evaluation System, demonstrate a good bond strength and surprisingly good water resistance. Several xylan dispersions fulfill the D1 and WATT 91 requirements for wood adhesives according to European Standards EN 204 and EN 14257, exhibiting good bond strength and heat resistance. Xylan dispersed in a poly(vinyl amine) solution also shows remarkable water resistance and reaches the threshold for the D2 criterion according to European Standard EN 204. [ABSTRACT FROM AUTHOR]

Abstract: We report a model system to control the dispersion and inter-particle distance of polymer-grafted Al2O3-nanoparticles in high molecular weight poly(ethylene-co-butyl acrylate). The proposed methods make it possible to extend the use of surface initiated atom transfer radical polymerization (SI-ATRP) in combination with more commercial grades of silanes and particles, showing the versatility of this polymerization process. The nanoparticles were surface-modified by an amine-terminated silane, forming multilayered silane coatings to which moieties capable of initiating ATRP were attached. Subsequently, “short” (DP: 117) and “long” (DP: 265) chains of poly(n-butyl acrylate) were grafted from the particles via SI-ATRP. The graft density was found to be in accordance with the density of the accessible amine groups and could therefore be assessed directly after the initial silanization step using UV–Vis spectrometry. From AFM micrographs, the grafted nanoparticles were found to be well-dispersed in the matrix. This observation was corroborated by a novel simulation method capable of transforming the inter-particle distances from 2D to 3D, for the closest and more distant neighbors. Further, we calculated the deviation ratios and concluded that the dispersions were homogeneous and that the inter-particle distances were related to the graft length. The homogeneous dispersions were explained by dominating enthalpic contributions of the polymer grafts to the nanocomposites in combination with shielding of the nanoparticle core–core attraction by the silane multilayer (similar to bimodal systems). [Copyright &y& Elsevier]

Highlights: [•] Gums can be used as binders for wood adhesives. [•] Locust bean gum dispersion fulfill the criteria for a D2 and WATT 91 wood adhesive. [•] Locust bean gum dispersions can be pressed at room temperature as well as at elevated temperatures. [ABSTRACT FROM AUTHOR]

Highlights: [•] Enzymatic hydrolysis or heat treatment of wheat gluten for enhanced adhesive properties. [•] SE-HPLC and 13C NMR analyses of modified wheat gluten. [•] Structural changes correlated with tensile shear strength measurements of wood substrates. [•] Mild hydrolysis: improved bond strength due to unfolding. [•] Heat treatment: improvement due to a combination of unfolding and polymerization. [Copyright &y& Elsevier]

Abstract: Soy protein isolate and wheat gluten were studied to evaluate their wood bonding performance. A multiscale approach was employed, combining tensile shear strength measurements, optical microscopy, and adhesion measurements at the nanoscale using atomic force microscopy. Tensile shear strength measurements were performed on beech wood substrates bonded with either dispersions of soy protein isolate or wheat gluten to investigate bond strength and water resistance. The results reveal a significant difference in bond strength between the plant proteins. Soy protein isolate is superior to wheat gluten, especially regarding water resistance, both under acidic and alkaline conditions. Cross sections of the wood substrates were examined by optical microscopy to study protein penetration and bond line thickness. The results indicate that a proper bond can be obtained using lower amount of soy protein isolate than wheat gluten. Atomic force microscopy in colloidal probe mode was used to investigate nanoscale adhesion between cellulose and solvent cast protein films. The results show that adhesion between the plant proteins and the wood component is important for the bonding performance. Further, it is shown that the results from atomic force microscopy and tensile shear strength measurements display the same trend demonstrating that the bonding properties translates well spanning regimes from the macro- to the nanoscale. The presented multiscale approach is shown to have great potential and may be used in the future to predict properties at different length scales in the design and formulation of new bioadhesives. [Copyright &y& Elsevier]

Abstract: In this work, the objective was to synthesize a compatibilizer that can electrostatically adsorb onto cellulose fibers, in fiber-based composites, to enhance the interaction between the fibers and non-polar polymer matrices. This physical route to attach the compatibilizer onto and thereby modify a fiber surface is convenient since it can be performed in water under mild conditions. Polystyrene (PS) was used for the high molecular weight, non-polar, block and poly(dimethylamino)ethyl methacrylate (PDMAEMA) was used as the polar block, which was subsequently quaternized to obtain cationic charges. The block copolymer self-assembles in water into cationic micelles and the adsorption to both silicon oxide surfaces and cellulose model surfaces was studied. The micelles spread out on the surface after heat treatment and contact angle measurements showed that the contact angles against water increased significantly after this treatment. AFM force measurements were performed with a PS probe to study the adhesive properties. The adhesion increased with increasing contact time for the treated surfaces, probably due to entanglements between the polystyrene blocks at the treated surface and the probe. This demonstrates that the use of this type of amphiphilic block copolymer is a promising route to improve the compatibility between charged reinforcing materials, such as cellulose-based fibers/fibrils, and hydrophobic matrices in composite materials. [Copyright &y& Elsevier]

Abstract: Interfacial adhesion between immiscible cellulose–polymer interfaces is a crucial property for fibrous biocomposites. To tailor the interfacial adhesion, the grafting of polymers from cellulose films was studied using ring-opening polymerization of ε-caprolactone. The poly(ε-caprolactone) (PCL) grafted cellulose was analyzed with FTIR, AFM and via water CA measurements. The graft length was varied by the addition of a free initiator, enabling tailoring of the interfacial toughness. Films of microfibrillated cellulose were grafted with PCL and hot-pressed together with a PCL-film to form a bilayer laminate. Interfacial peeling toughness correlates very strongly with PCL degree of polymerization (DP). PCL grafts form physical entanglements in the PCL matrix and promote significant plastic deformation in the PCL bulk, thus increasing interfacial peeling energy. [ABSTRACT FROM AUTHOR]

Abstract: This study demonstrates the surface modification of thermally expandable core/shell microspheres by grafting glycidyl methacrylate (GMA) using activators regenerated by electron transfer (ARGET) ATRP. To retain the expansion properties it was essential to minimize the shear forces, use solvents compatible with the microspheres and keep the reaction times short (three hours or less). Using microspheres with hydroxyl groups on the surface, it was found that after converting these to α-bromo esters, GMA could be grafted by ARGET ATRP using only 50ppm of copper catalyst in toluene at 30°C. Decent control of the polymerization was achieved with PMDETA as ligand reaching PDIs of 1.4 for the solution polymerization of GMA. When microspheres were present, the polymerization was less controlled with higher PDIs. The epoxide groups of the grafted microspheres were hydrolyzed by HCl in THF providing a hydrophilic surface of the microsphere. The expansion property of the microspheres was studied after each reaction step by thermal mechanical analysis, and it was found that the expansion capacity was well preserved with only limited negative effect on the microspheres. [Copyright &y& Elsevier]

Abstract: In cellulose nanocomposites, the surface of the nanocellulosic phase is critical with respect to nanocellulose dispersion, network formation and nanocomposite properties. Microfibrillated cellulose (MFC) has been grafted with poly(ε-caprolactone) (PCL), via ring-opening polymerization (ROP). This changes the surface characteristics of MFC and makes it possible to obtain a stable dispersion of MFC in a nonpolar solvent; it also improves MFC’s compatibility with PCL. The thermal behavior of MFC grafted with different amount of PCL has been investigated using thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC). From TGA measurements, the fraction of PCL in MFC-PCL samples was estimated to 16%, 19%, and 21%. The crystallization and melting behavior of free PCL and MFC-PCL were studied with DSC, and a significant difference was observed regarding melting points, crystallization temperature, degree of crystallinity, as well as the time required for crystallization. [Copyright &y& Elsevier]

Metal complexes of chiral oxazoline derivatives immobilized on soluble as well as insoluble supports serve as versatile asymmetric catalysts in a variety of applications. In a few cases recovery and reuse of the chiral ligands have been achieved. [Copyright &y& Elsevier]