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ObjectiveTo compare the short-term, mid-term and long-term effects between three interventions (education only, education and strengthening exercises, education and motor control exercises) for rotator cuff-related shoulder pain (RCRSP) on symptoms and function.Methods123 adults presenting with RCRSP took part in a 12-week intervention. They were randomly assigned to 1 of 3 intervention groups. Symptoms and function were evaluated at baseline and at 3 weeks, 6 weeks, 12 weeks and 24 weeks using the Disability of Arm, Shoulder and Hand Questionnaire (QuickDASH) (primary outcome) and Western Ontario Rotator Cuff Index (WORC). Linear mixed modelling was used to compare the effects of the three programmes on the outcomes.ResultsAfter 24 weeks, between-group differences were −2.1 (-7.7 to 3.5) (motor control vs education), 1.2 (-4.9 to 7.4) (strengthening vs education) and −3.3 (-9.5 to 2.8) (motor control vs strengthening) for theQuickDASH and 9.3 (1.5 to 17.1) (motor control vs education), 1.3 (−7.6 to 10.2) (strengthening vs education) and 8.0 (−0.5 to 16.5) (motor control vs strengthening) for the WORC. There was a significant group-by-time interaction (p=0.04) withQuickDASH, but follow-up analyses did not reveal any clinically meaningful between-group differences. There was no significant group-by-time interaction (p=0.39) for the WORC. Between-group differences never exceeded the minimal clinically important difference ofQuickDASH or WORC.ConclusionIn people with RCRSP, the addition of motor control or strengthening exercises to education did not lead to larger improvements in symptoms and function compared with education alone. Further research should investigate the value of providing stepped care by identifying individuals who may only need education and those who would benefit from the addition of motor control or strengthening exercises.Trial registration numberNCT03892603.

The objective of this study was to compare the effects of a cervicovestibular rehabilitation program combined with symptom-limited aerobic exercise (SLAE) program to a SLAE program alone in adults with persistent symptoms after mild traumatic brain injury (mTBI) on severity of symptoms and other indicators of clinical recovery. In this single-blind, parallel-group randomized controlled trial, 60 adults with persistent symptoms after mTBI were randomly assigned to: (1) a 6-week SLAE program or (2) a 6-week cervicovestibular rehabilitation program combined with a SLAE program. All participants took part in four evaluation sessions (baseline, week 6, 12, and 26) performed by a blinded evaluator. The primary outcome was the Post-Concussion Symptoms Scale (PCSS). The secondary outcomes were Numerical Pain Rating Scale (NPRS), Neck Disability Index (NDI), Headache Disability Inventory (HDI), Dizziness Handicap Inventory (DHI), time to return to function, and physical cervical and vestibular measures. Non-parametric analysis for longitudinal data was used to evaluate the effect of interventions on outcomes. For PCSS, NPRS, NDI, HDI, DHI, and return to function, there were no group-by-time interactions at any time points follow-up (

Objectives Respiratory diseases are the leading cause of hospitalization in Nunavik (northern Québec, Canada) and contribute to disparities in life expectancy with the rest of Canada. As part of Qanuilirpitaa? 2017, a cross-sectional population-based health survey, we sought to describe the prevalence of respiratory health indicators, including the first estimate of airway obstruction based on spirometry in an Inuit population, and explore their associated characteristics. Methods We analyzed data from 1296 participants aged 16 years and older, using multivariate logistic regression to assess characteristics associated with spirometry-determined airway obstruction and self-reported respiratory symptoms, i.e., wheezing in the last year and chronic cough during at least 3 months. Results In this relatively young population (83% aged 16 to 54), the prevalences of wheezing, chronic cough, and airway obstruction were, respectively, 27% (95% CI 24–30), 21% (18–23), and 17% (14–20). These estimates are prone to biases due to the relatively low participation rate (about 37%). The most consistent associations were with smoking (≥ 15 pack-years; odds ratio [OR] 3.13, 3.39, and 2.86 for the three indicators, respectively) and food security (OR 0.55 with wheezing and OR 0.26 with chronic cough), as defined in the Household Food Security Survey Module. Wheezing was also associated with allergic sensitization to dogs (2.60) and obesity (2.18). Chronic cough was associated with respiratory infections during childhood (2.12), housing in need of major repairs (1.72), and housing crowding (1.50), and was negatively associated with participation to traditional activities (0.62) and going on the land (0.64). Airway obstruction was associated with being underweight (3.84) and post-secondary education (0.40). Among young adults and women, wheezing was also associated with any inhalation of solvents for recreational purposes during their lifetime (2.62 and 1.56, respectively), while airway obstruction was associated with regular marijuana use (2.22 and 1.84, respectively). Conclusion Smoking and food insecurity are both highly prevalent and strongly associated with respiratory symptoms in Nunavik. Together with essential smoking prevention and cessation programs, our findings suggest that solving food security and housing crises, improving socioeconomic conditions, and promoting traditional lifestyle may improve respiratory health in Nunavik.

The objectives of this study were to translate the Pain Self-Efficacy Questionnaire (PSEQ) into Canadian French (PSEQ-F) and to evaluate its validity, reliability and responsiveness in a French-Canadian sample of patients with persistent rotator cuff related shoulder pain (RCRSP).Translation and cross-cultural adaptation of the original English version of the PSEQ into Canadian French were performed according to standard procedures. Thereafter, 78 adults with RCRSP completed the PSEQ-F on three occasions: baseline, 2 days later to evaluate the reliability and 6 weeks later to evaluate responsiveness.Cross-cultural adaptation was performed without problems with content or language. The PSEQ-F was found to be reliable (Intraclass Correlation Coefficient = 0.96; Minimal Detectable Change = 3 points [5%]), valid (moderate correlations with an abbreviated version of Disability of the Arm, Shoulder and Hand [The PSEQ-F is a reliable, valid and responsive questionnaire that can be used to assess pain self-efficacy in French-speaking individuals with RCRSP. Further studies should use a self-efficacy-specific Global Rating of Change scale to estimate its responsiveness more thoroughly.Implications for rehabilitationHigher levels of pain self-efficacy have been associated with increased odds of symptom resolution in those with persistent rotator cuff related shoulder pain (RCRSP).The Pain Self-Efficacy Questionnaire (PSEQ) has been identified as the most frequently used tool by clinicians to assess pain self-efficacy in patients at risk of developing persistent musculoskeletal pain.The Canadian French version of the PSEQ (PSEQ-F) is a reliable, valid and responsive questionnaire that can be used to assess pain self-efficacy in French-speaking individuals with RCRSP.

INTRODUCTION Approximately 25% of people with sport-related concussion (SRC) experiences persistent symptoms. The 2016 Berlin consensus on SRC recommends symptom-limited aerobic exercise as a rehabilitation option for persistent symptoms after concussion. However, this recommendation is based on a limited body of knowledge because there is uncertainty about the effectiveness of such interventions. The objective of this systematic review is to assess the effects of symptom-limited aerobic exercise programs compared with control interventions on symptom intensity in individuals with SRC. METHODS A structured search was conducted in MEDLINE, EMBASE, CINHAL, and EBM reviews. Randomized clinical trials (RCT) including aerobic exercise programs as an intervention for SRC were included. After selection, the risk of bias and Grading of Recommendations, Assessment, Development and Evaluation recommendations were applied to pooled studies for quantitative analysis. Standard mean differences (SMD) and 95% confidence interval (CI) were calculated. A descriptive analysis was also performed. RESULTS Seven RCT (326 participants) in adolescent populations were included. Three of seven RCT had a high risk of bias. Symptom-limited aerobic exercise programs have a significant beneficial effect on the perception of symptoms (6 studies, 277 participants, low-quality evidence; pooled SMD, -0.44; 95% CI, -0.68 to -0.19). When introduced in the acute phase, symptom-limited aerobic exercise programs have a significant beneficial effect on symptomatic recovery compared with control interventions (3 studies, 206 participants, moderate quality evidence, pooled SMD, -0.43; 95% CI, -0.71 to -0.15). CONCLUSIONS Symptom-limited aerobic exercise programs are beneficial in improving symptoms of adolescents after an SRC. Good-quality studies are needed to determine effects on adults and on other outcomes.

This study investigated the properties of films or bioplastics fabricated using a wet processing method from yellow pea protein isolate (YPI) and protein concentrate (YPC) for potential application in food packaging. The wet processing method included mixing the protein with water and glycerol followed by casting and drying the films in a humidity- and temperature-controlled chamber. Whey protein isolate (WPI) and a film from a blend of equal amounts of YPI and WPI, labelled as YPI + WPI, were also studied. Fourier transform-infra red analysis revealed that films from YPI, YPC, WPI and YPI + WPI were formed by protein polymerisation with the plasticiser, glycerol, via hydrophobic and hydrophilic interactions. The protein films had contact angles of YPC > YPI + WPI > YPI, whereas the mechanical and thermal resilience of films formulated from YPI, YPC and the protein blend were comparable to the properties of WPI-based films. The findings demonstrate that yellow pea proteins can be used as biomaterials to develop protein and protein-blend films or bioplastics for food packaging and edible applications.

Starch nanoparticles (SNP) were modified with synthetic polymers using the “grafting to” approach and nitroxide-mediated polymerization. SG1-capped poly(methyl methacrylate-co-styrene) (P(MMA-co-S)...

The Pain Self-Efficacy Questionnaire has excellent validity, reliability, and responsiveness. Further high-quality studies are needed to determine responsiveness in populations other than chronic low back pain., A higher level of pain self-efficacy has been suggested as a predictor of a better outcome in patients with musculoskeletal disorders. The Pain Self-Efficacy Questionnaire (PSEQ) is one of the most frequently used patient-reported outcome measures for pain self-efficacy. The purpose of this study was to conduct a systematic review that would identify, appraise, and synthetize the psychometric properties of the PSEQ. Embase, MEDLINE, and CINAHL databases were searched for publications reporting on psychometric properties of the PSEQ in populations with musculoskeletal disorders. After applying selection criteria on identified citations, 28 studies (9853 participants) were included. The methodological quality as measured with the COSMIN risk of bias tool varied from adequate to very good for most measurement properties. The results showed a weighted mean intraclass correlation coefficient of 0.86 (range: 0.75–0.93) for test–retest reliability for the original 10-item PSEQ and the minimal detectable change at 95% confidence interval was 11.52 out of 60 points. Effect size and standardized response mean values were 0.53 and 0.63, respectively, whereas the minimal clinically important difference ranged from 5.5 to 8.5 in patients with chronic low back pain. Internal consistency (Cronbach alpha) ranged from 0.79 to 0.95. The results also showed that the PSEQ has low to moderate correlations with measures of quality of life, disability, pain, pain interference, anxiety, depression, and catastrophizing. Finally, the PSEQ has been adapted and validated in 14 languages. Overall, the results demonstrate that the PSEQ has excellent validity, reliability, and responsiveness. Further high-quality studies are needed to determine responsiveness in populations other than chronic low back pain.

Cellulose nanocrystals (CNCs) are naturally-sourced nanoparticles that can be used to modify polymers and provide exceptional mechanical properties to nanocomposite materials. In this study, CNCs were incorporated into water-based pressure sensitive adhesives (PSAs) via in situ semi-batch emulsion polymerization to improve PSA properties. A sequential design approach was used to improve CNC/poly(n-butyl acrylate/vinyl acetate) nanocomposite PSAs. In the first part of the design, the effects of acrylic acid (AA) and anionic surfactant sodium dodecyl sulfate (SDS) were examined in the presence of 0.5 wt% CNCs (based on polymer mass). While the SDS was crucial to maintaining latex stability, its excessive addition led to a decrease in PSA performance, namely tack and peel strength. The AA comonomer was pivotal in improving the shear strength of the PSAs, especially in the presence of CNCs. In all cases, the addition of CNCs led to improved PSA shear strength. In the second part of the design, the addition of 1-dodecanethiol (NDM) as a chain transfer agent (CTA) with CNC levels up to 1 wt% led to an improvement in tack and peel strength but at the cost of diminishing the shear strength. Generally, the addition of CNCs improved PSA performance. Thus, to maximize the impact of CNCs on PSA properties, a careful balance of SDS (for latex stability), AA (to improve shear strength) and NDM (to improve tack and peel strength) are needed.

Modification of starch nanoparticles (SNP) was conducted with styrene oxide (STO) to change their hydrophilic/hydrophobic character. Unmodified SNP and modified SNP-STO were investigated as Pickering stabilizers in miniemulsion polymerization and emulsion polymerization. The influence of varying the degree of substitution (DS) was explored in terms of interfacial activity with saturated analogues of the monomers used to prepare the miniemulsions. Pickering miniemulsion stability tests conducted with styrene, methyl methacrylate and butyl acrylate showed no apparent coalescence when using SNP-STO (DS 0.10). Pickering miniemulsion polymerization results (using the oil-soluble Vazo-52 initiator) suggest a synergistic stabilization effect between styrene and SNP-STO due to interactions between the aromatic rings present on both styrene and modified SNP-STO. Pickering emulsion polymerizations prepared using persulfate initiator and SNP-STO exhibited additional colloidal stability compared to the miniemulsions, likely provided by the persulfate anions.

Cold water-soluble starch (CWS) is a polysaccharide that is industrially important for several applications including paper coatings, but the high viscosity of starch solutions limits the amount of starch that can be incorporated in many applications. Due to the poor mechanical properties of starch and poor dispersibility of starch in hydrophobic matrices, it is often chemically modified to make it more useful. Herein, we report the first grafting from (co)polymerisation of CWS via nitroxide-mediated polymerisation (NMP) of methyl methacrylate-co-styrene, methyl acrylate, and acrylic acid. Our three step approach consists of: (1) modification of CWS with 4-vinylbenzyl chloride; (2) functionalisation with 2-methyl-2-[N-tertbutyl-N-(diethoxy-phosphoryl-2,2-dimethylpropyl)-aminoxy] propionic acid initiator; and (3) grafting from (co)polymerisation via NMP. The (co)polymerisations were well controlled showing linear reaction kinetics for all monomers and relatively low dispersities (

A return to running after anterior cruciate ligament reconstruction (ACL-R) is critical to the clinical success of any cutting and pivoting athlete who wishes to return to sport. Knowledge of specific alterations during running after ACL-R is required to optimise rehabilitation for improving outcomes and long-term disability. The objective of this systematic review was to summarise kinematic, kinetic and muscle activation data during running after ACL-R and the intrinsic factors (e.g. surgical technique and strength asymmetries) affecting running biomechanics. MEDLINE, EMBASE, SPORTDiscus and CINAHL databases were searched from inception to 10 December, 2018. The search identified studies comparing kinematic, kinetic or muscle activation data during running between the involved limb and contralateral or control limbs. Studies analysing the effect of intrinsic factors in the ACL-R group were also included. Risk of bias was assessed, qualitative and quantitative analyses performed, and levels of evidence determined. A total of 1993 papers were identified and 25 were included for analysis. Pooled analyses reported a deficit of knee flexion motion and internal knee extension moment, compared with both contralateral or control limbs, during the stance phase of running from 3 months to 5 years after ACL-R (strong evidence). Inconsistent results were found for both peak vertical ground reaction force and impact forces after ACL-R. Patellofemoral and tibiofemoral joint contact forces differed from both contralateral or control limbs up until at least 2.5 years after ACL-R and moderate evidence indicated no difference for muscle activations during moderate speed running. Quadriceps and hamstring strength asymmetries, and knee function, but not surgical techniques, were likely to be associated with both knee kinematics and kinetics during running after ACL-R. After ACL-R, knee flexion motion and internal knee extension moment are the most affected variables and are consistently smaller in the injured limb during running when pooling evidence. Clinicians should be aware that these deficits do not appear to resolve with time and, thus, specific clinical interventions may be needed to reduce long-term disability. Registered in PROSPERO 2017, CRD42017077130.

Starch nanoparticles (SNPs) were used to partially replace petroleum-based polymers in a biobased latex adhesive application. Modification of SNPs (i.e., increasing cross-link density, functionalizing using a sugar-based monomer, and tuning SNP hydrophobicity) was performed prior to their incorporation in a semibatch emulsion polymerization to produce stable SNP-based latexes. SNP loadings and latex solids content were varied to study their effect on latex stability and properties (e.g., viscosity, particle size, adhesive properties, particle morphology). Stable and low viscosity latexes with up to 45 wt % SNP loadings and 55 wt % latex solids were achieved. STEM images confirmed the presence of the core–shell morphology, where SNPs were located in the particle cores and provided biocontent, while the acrylic polymers were present as the shell and governed the application properties. Pushing the limits of SNP loading and latex solids was shown to come at a cost to adhesive and other properties.

Emulsion polymerized latex-based pressure-sensitive adhesives (PSAs) are more environmentally benign because they are synthesized in water but often underperform compared to their solution polymerized counterparts. Studies have shown a simultaneous improvement in the tack, and peel and shear strength of various acrylic PSAs upon the addition of cellulose nanocrystals (CNCs). This work uses atomic force microscopy (AFM) to examine the role of CNCs in (i) the coalescence of hydrophobic 2-ethyl hexyl acrylate/ n -butyl acrylate/methyl methacrylate (EHA/BA/MMA) latex films and (ii) as adhesion modifiers over multiple length scales. Thin films with varying solids content and CNC loading were prepared by spin coating. AFM revealed that CNCs lowered the solids content threshold for latex particle coalescence during film formation. This improved the cohesive strength of the films, which was directly reflected in the increased shear strength of the EHA/BA/MMA PSAs with increasing CNC loading. Colloidal probe AFM indicated that the nano-adhesion of thicker continuous latex films increased with CNC loading when measured over small contact areas where the effect of surface roughness was negligible. Conversely, the beneficial effects of the CNCs on macroscopic PSA tack and peel strength were outweighed by the effects of increased surface roughness with increasing CNC loading over larger surface areas. This highlights that CNCs can improve both cohesive and adhesive PSA properties; however, the effects are most pronounced when the CNCs interact favourably with the latex polymer and are uniformly dispersed throughout the adhesive film. This article is part of the theme issue ‘Bio-derived and bioinspired sustainable advanced materials for emerging technologies (part 1)’.

Protein-based bioplastics have attracted great interest owing to their sustainable sources, biodegradability and safe use for food and pharmaceutical applications. Sources of dietary proteins are ubiquitous and include, but are not limited to, microalgae, legumes, pulses, cereals, insects and dairy products. Dietary proteins have structural features that confer unique properties and functionalities in the formation of biodegradable bioplastics. Bioplastics can be formed from dietary proteins through two main techniques, wet processing and dry processing. Dietary proteins can be modified with suitable chemistries and additives to enhance their features such as aesthetics and mechanical, thermal, chemical and antimicrobial properties. Further, the properties of bioplastics can be altered based on processing parameters such as pH, temperature, concentration, type of protein precursors and plasticizers. In this chapter, a comprehensive discussion of dietary proteins and their physicochemical properties as suitable alternatives for the formation of bioplastics is presented. The potential of using protein bioplastics as edible and active packages is also discussed.

The main objective of a 2012-2013 clinical study on the oral health of Quebec elementary school students was to assess the oral health status of Grade 2 and Grade 6 students. We assessed various stages of caries and created caries indicators for primary and permanent dentitions combined.Oral health examination of 2875 Grade 2 students and 2788 Grade 6 students, enrolled in public and private, French- and English-language schools, was carried out at schools. The examinations were performed by 16 trained and calibrated dentists using International Caries Detection and Assessment System (ICDAS) II criteria. A 3-level sampling design ensured that the study was representative for the province of Quebec.Mean indexes for decayed, missing, filled primary teeth (dmft) and secondary teeth (DMFT) or surfaces (dmfs and DMFS) for all stages of caries were as follows. Grade 2 students: dmft 3.96, DMFT 1.88, dmft + DMFT 5.84, dmfs 8.33, DMFS 2.96 and dmfs + DMFS 11.28. Grade 6 students: dmft 1.94, DMFT 4.98, dmft + DMFT 5.98, dmfs 4.04, DMFS 7.86 and dmfs + DMFS 9.96. Most students (90% for Grade 2 and 92% for Grade 6) had a dmfs + DMFS0.Tooth decay remains a public health problem in Quebec. The findings testify to the importance of reinforcing preventive measures to better control dental caries among youth. It is advantageous to use ICDAS II in the context of oral health surveillance at a population level and to present the results as a combination of primary and permanent dentitions.

IntroductionLifetime prevalence of shoulder pain is 70%, and approximately 50% of people with shoulder pain will experience pain for more than a year. Rotator cuff-related shoulder pain (RCRSP) is the most common shoulder condition and the main non-surgical intervention is exercise therapy. For approximately 30% of people with RCRSP, this approach does not lead to a significant reduction in symptoms. This may be due to an inappropriate dosage or choice of exercises. The aim of this investigation is to compare the short, mid and long-term effects, in terms of symptoms, functional limitations, kinesiophobia and pain catastrophising, of three different shoulder rehabilitation approaches (education, strengthening, motor control) in adults with RCRSP.Methods and analysisIn this single-blind (assessor), parallel-group, randomised clinical trial, 123 adults presenting with RCRSP will take part in a 12-week rehabilitation programme. They will be randomly assigned to one of three groups (education only, strengthening approach or motor control-focused approach). Abbreviated version of the Disabilities of the Arm, Shoulder and Hand Questionnaire, the primary outcome, Western Ontario Rotator Cuff Index and Brief Pain Inventory will evaluate symptoms and functional limitations, while Tampa Scale of Kinesiophobia and Pain Catastrophizing Scale will evaluate pain-related fear and catastrophising at baseline and at 3, 6, 12 and 24 weeks. Ultrasonographic acromiohumeral distances and tendon thickness will be assessed at baseline and 12 weeks. Intervention groups will be compared on outcomes with intention-to-treat analyses using two-way repeated measures analysis of variance if the data are normally distributed or non-parametric analysis of longitudinal data if they are not.Ethics and disseminationEthics approval was obtained from the Sectorial Rehabilitation and Social Integration Research Ethics Committee of the Centre Intégré Universitaire de Santé et de Services Sociaux de la Capitale Nationale (CIUSSS-CN). Results will be disseminated through international publications in peer-reviewed journals, in addition to international conference presentations.Trial registration numberNCT03892603.

Nanocelluloses (i.e., bacterial nanocellulose, cellulose nanocrystals, and cellulose nanofibrils) are cellulose-based materials with at least one dimension in the nanoscale. These materials have unique and useful properties and have been shown to assemble at oil-water interfaces and impart new functionality to emulsion and latex systems. Herein, the use of nanocellulose in both emulsions and heterogeneous water-based polymers is reviewed, including dispersion, suspension, and emulsion polymerization. Comprehensive tables describe past work employing nanocellulose as stabilizers or additives and the properties that can be tailored through the use of nanocellulose are highlighted. Even at low loadings, nanocellulose offers an unprecedented level of control as a property modifier for a range of emulsion and polymer applications, influencing, for example, emulsion type, stability, and stimuli-responsive behavior. Nanocellulose can tune polymer particle properties such as size, surface charge, and morphology, or be used to produce capsules and polymer nanocomposites with enhanced mechanical, thermal, and adhesive properties. The role of nanocellulose is discussed, and a perspective for future direction is presented.

Starch nanoparticles (SNPs) are chosen as renewable alternatives to partially replace petroleum-based monomers and produce bio-based latexes for adhesive applications. To maintain adhesive performance, SNPs are modified (i.e., via increasing cross-link density, vinyl functionalization, and adjusting hydrophilic/hydrophobic balance) to facilitate their incorporation into the latex particles. The modified SNPs are then polymerized in a semi-batch emulsion polymerization at 60 °C, and yield low viscosity latexes with up to 17 wt% SNP loading and 42 wt% solids. TEM/STEM imaging is performed and reveals the presence of a core-shell particle morphology. This is supported by comparing the adhesive properties of SNP-containing latex films from an in situ preparation vs. a blend of acrylic latex with SNPs. The results suggest that the modified SNPs were largely encapsulated into the latex particles rather than in the aqueous phase or at the latex particle/water interface.

Surface-initiated atom transfer radical polymerization was used to graft hydrophobic poly(butyl acrylate) from cellulose nanocrystals (CNCs) resulting in compatibilized CNCs that were successfully incorporated inside the core of polymer latex particles. CNCs are anisotropic nanoparticles derived from renewable resources and have potential as reinforcing agents in nanocomposites. However, challenges due to the incompatibility between cellulose and hydrophobic polymers and processing difficulties, such as aggregation, have limited the performance of CNC nanocomposites produced to date. Here, CNCs were incorporated into the miniemulsion polymerization of methyl methacrylate by adding polymer-grafted CNCs to the monomer phase. A poly(methyl methacrylate)-CNC nanocomposite latex was subsequently produced in situ, whereby polymer-grafted CNCs (with optimized graft length) were located inside the latex particles, as shown by transmission electron microscopy. This work provides a method for controlling the location of CNCs in latex-based nanocomposites and may extend the use of CNCs in commercial adhesives and coatings.

The impact of cellulose nanocrystals (CNCs) as a property modifier for pressure sensitive adhesives (PSAs) was investigated. Stable CNC/poly(n-butyl acrylate-co-methyl methacrylate) latex nanocomposites with different CNC loadings ranging from 0.25 to 1 wt% (based on monomer weight) were synthesized by both an in situ seeded semi-batch polymerization and a blending technique. The PSA films obtained from both techniques demonstrated a concurrent enhancement of shear strength, tack, and peel strength with increasing CNC content. However, the performance enhancement for the PSAs prepared via the in situ technique was substantially greater: increases of up to 3.8x for tack, 6x for peel strength and 20x for shear strength for the in situ technique compared to increases of up to 2.4x for tack, 1.5x for peel strength and 6.4x for shear strength for the blending technique. The difference in mechanical performance of the CNC/PSA films synthesized via the in situ technique vs. blending was a result of better interaction of CNCs with the polymer matrix during both latex synthesis and film formation.

A kinetic model for the redox-initiated radical telomerization of vinyl acetate activated by microwave irradiation is presented. Four approaches based on the “microwave” or “thermal” effects were u...

Cellulose nanocrystals (CNCs) are sustainable rigid rod-shaped nanoparticles that have potential as reinforcing agents in polymer nanocomposites. CNCs can also act as Pickering stabilizers in emulsions and foams due to their amphiphilic nature. In this work, CNCs were rendered surface active through adsorption with the biopolymer methyl cellulose (MC) to produce MC-coated CNCs. MC-coated CNCs were used to stabilize the microsuspension polymerization of methyl methacrylate. Monomer conversion, latex size, and gel content were studied. The microsuspension polymerization resulted in a double morphology where poly(methyl methacrylate) (PMMA) microparticles and nanoparticles were produced simultaneously. The ratio of micro- to nanoparticles could be tuned based on the CNC:MC ratio. Most nanoparticles were attached to the microparticles offering hierarchically structured latexes, although approximately 2 wt % were free in suspension. Drying conditions could be used to control the surface roughness of the dry la...

Core-shell latex-based pressure-sensitive adhesives comprising n-butyl acrylate, styrene and acrylic acid were prepared via two-stage seeded semi-batch emulsion polymerization. d-Limonene (Lim) was used as a renewable chain transfer agent. Adhesive performance was modified by manipulating the microstructure of both the latex particle cores and shells. In the first stage of the polymerization, the concentrations of Lim and divinylbenzene (DVB) crosslinker were varied to alter the core microstructure and thus, the cohesive strength of the adhesive films. The particle shell microstructure was modified in the second stage of the polymerization by varying only the amount of Lim. As a result, a variety of particle microstructures and morphologies were generated. Tack and peel strength decreased with increasing Lim concentration while shear strength showed a maximum at a moderate core Lim concentration of 2 phm. Empirical models were developed using stepwise regression to correlate tack, peel strength and shear strength to Lim concentration in the core/shell and DVB concentration in the core.

Starch nanoparticles (SNP) are attracting increased attention as a renewable bio-based alternative to petroleum-based polymers in the materials community. In this work, we describe the grafting from of SNP with synthetic polymers via nitroxide-mediated polymerization (NMP). Varying amounts of poly(methyl methacrylate-co-styrene) (P(MMA-co-S)), poly(methyl acrylate) (PMA) and poly(acrylic acid) (PAA) were grafted from the surface of SNP in a three-step process. The grafting of synthetic polymers from the surface of SNP was confirmed by FTIR, 1H NMR, elemental analysis and thermogravimetric analysis. These new tailor-made starch-based hybrid materials could find use in paper coatings, adhesives, paints, as well as in polymer latex applications.

Multi-component polymers can provide many advantages over their homopolymer counterparts. Terpolymers are formed from the combination of three unique monomers, thus creating a new material that will exhibit desirable properties based on all three of the original comonomers. To ensure that all three comonomers are incorporated (and to understand and/or predict the degree of incorporation of each comonomer), accurate reactivity ratios are vital. In this study, five terpolymerization studies from the literature are revisited and the &lsquo, ternary&rsquo, reactivity ratios are re-estimated. Some recent studies have shown that binary reactivity ratios (that is, from the related copolymer systems) do not always apply to ternary systems. In other reports, binary reactivity ratios are in good agreement with terpolymer data. This investigation allows for the comparison between previously determined binary reactivity ratios and newly estimated &lsquo, reactivity ratios for several systems. In some of the case studies presented herein, reactivity ratio estimation directly from terpolymerization data is limited by composition restrictions or ill-conditioned systems. In other cases, we observe similar or improved prediction performance (for ternary systems) when &lsquo, reactivity ratios are estimated directly from terpolymerization data (compared to the traditionally used binary reactivity ratios). In order to demonstrate the advantages and challenges associated with &lsquo, reactivity ratio estimation, five case studies are presented (with examples and counter-examples) and troubleshooting suggestions are provided to inform future work.

Free radical emulsion terpolymerizations of conjugated linoleic acid (CLA), styrene (Sty), and butyl acrylate (BA) were performed at 80 °C. Terpolymers were characterized for composition, conversion, molecular weight and glass transition temperature, latexes were characterized for viscosity and particle size while adhesives were characterized for tack, peel strength, shear strength, storage modulus, loss modulus and tan delta. One impurity commonly found in CLA, oleic acid, was shown to influence the reaction kinetics significantly. Adhesive performance was tuned using divinylbenzene (DVB) crosslinker to keep the terpolymer molecular weight in a desired range. By using a constrained mixture design, the influence of terpolymer composition, chain transfer agent (CTA) concentration, DVB concentration, molecular weights, viscosity and particle size on tack, peel strength and shear strength was investigated. The final forms of the resulting empirical models allowed the creation of 3D response surfaces for pressure sensitive adhesive (PSA) performance optimization.

Poly(sodium acrylate) (PNaA) based nanocomposites were synthesized using different nanosilver loadings via redox solution polymerization at room temperature and under full exposure to the atmosphere. The nanocomposites exhibited increasing antibacterial activity with increased nanosilver content. Biocompatibility was determined using an MTT assay; no significant cytotoxicity was observed at the examined nanosilver loadings. Adhesion was measured using a tensile test and the stress versus strain curve showed an acceptable stress development in the model tissue using bioadhesive containing 2 wt% nanosilver. Introducing a second, more degradable polymer to the system as an interpenetrating polymer network enabled tuning the bioadhesive degradation rate.

Cellulose nanocrystals (CNCs), a sustainable nanomaterial, are in situ incorporated into emulsion-based pressure-sensitive adhesives (PSAs). Commercially available CNCs with different surface hydrophilicity and surface charge (CNC101 and CNC103 from CelluForce) are used to explore their role in PSA property modification. Viscosity measurements and atomic force microscopy reveal differences in degree of association between the CNCs and the latex particles depending on the surface properties of the CNCs. The more hydrophilic and higher surface charge CNCs (CNC101) show less association with the latex particles. Dynamic strain sweep tests are used to analyze the strain-softening of the nanocomposites based on CNC type and loading. The CNC101 nanocomposites soften at lower strains than their CNC103 counterparts. This behavior is confirmed via dynamic frequency tests and modeling of the nanocomposites' storage moduli, which suggest the formation of CNC aggregates of, on average, 3.8 CNC101 and 1.3 CNC103 nanoparticles. Finally, PSA properties, i.e., tack, peel strength, and shear strength, simultaneously increase upon addition of both CNC types, although to different extents. The relationship between the PSA properties and CNC surface properties confirms that the less hydrophilic CNCs lead to improved CNC dispersion in the PSA films and therefore, enhance PSA properties.