AFM probing of polymer/nanofiller interfacial adhesion and its correlation with bulk mechanical properties in a poly(ethylene terephthalate) nanocomposite.

The interfacial adhesion between polymer and nanofiller plays an important role in affecting the properties of nanocomposites. The detailed relationship between interfacial adhesion and bulk properties, however, is unclear. In this work, we developed an atomic force microscopy (AFM)-based abrasive scanning methodology, as applied to model laminate systems, to probe the strength of interfacial adhesion relevant to poly(ethylene terephthalate) (PET)/graphene or clay nanocomposites. Graphite and mica substrates covered with ∼2 nm thick PET films were abrasively sheared by an AFM tip as a model measurement of interfacial strength between matrix PET and dispersed graphene and clay, respectively. During several abrasive raster-scan cycles, PET was shear-displaced from the scanned region. At temperatures below the PET glass transition, PET on graphite exhibited abrupt delamination (i.e., full adhesive failure), whereas PET on mica did not; rather, it exhibited a degree of cohesive failure within the shear-displaced layer. Moreover, 100-fold higher force scanning procedures were required to abrade through an ultimate "precursor" layer of PET only ∼0.2-0.5 nm thick, which must be largely disentangled from the matrix polymer. Thus, the adhesive interface of relevance to the strength of clay-filler nanocomposites is between matrix polymer and strongly bound polymer. At 90 °C, above the bulk PET glass transition temperature, the PET film exhibited cohesive failure on both graphite and mica. Our results suggest that there is little difference in the strength of the relevant interfacial adhesion in the two nanocomposites within the rubbery dynamic regime. Further, the bulk mechanical properties of melt mixed PET/graphene and PET/clay nanocomposites were evaluated by dynamic mechanical analysis. The glassy dynamic storage modulus of the PET/clay nanocomposite was higher than that of PET/graphene, correlating with the differences in interfacial adhesion probed by AFM.

PET/Graphene Compatibilization for Different Aspect Ratio Graphenes via Trimellitic Anhydride Functionalization.

Two trimellitic anhydride-functionalized, thermally reduced graphenes with different aspect ratios, A f, and the same C/O ratio (8:1) were prepared and melt-mixed into poly(ethylene terephthalate) (PET), and the mechanical properties of the resulting nanocomposites were studied with a focus on plastic deformation behavior. A slight increase in the G' of the melt was observed for the surface-modified low-A f graphene composites (A f = 20) below the percolation threshold, whereas a significant enhancement in G' was observed for higher-A f graphene composites (A f = 80) at all graphene loadings, both below and above the percolation concentration. Furthermore, the use of modified low-A f graphene caused an improvement both in Young's modulus and elongation at break of the resulting PET nanocomposites because of enhancement of interfacial adhesion between filler and matrix which resulted in the formation of a coupled network via covalent bonding and the suppression both of strain-induced orientation and strain-induced crystallization. By contrast, the use of modified higher-A f surface graphene in nanocomposites caused a drastic improvement in Young's modulus but lower elongation-at-break than with the unmodified counterpart; the former effect is due to the formation of denser coupled networks and stronger interfacial adhesion as a result of graphene surface modification and the latter is due to the added geometrical restriction in unentangling chains from the PET matrix in the presence of higher-A f graphene. The preceding observations demonstrate the potential impacts of tuning both surface chemistry and aspect ratio of graphene in the fabrication of PET/graphene composites.

Higher-Order Structure in Amorphous Poly(ethylene terephthalate)/Graphene Nanocomposites and Its Correlation with Bulk Mechanical Properties.

Graphene of two different aspect ratios, A f, was melt mixed with poly(ethylene terephthalate) (PET) to form amorphous PET/graphene composites with less than 5% crystallinity. The higher-order structure and mechanical properties of poly(ethylene terephthalate) (PET) in these composites were investigated using techniques such as differential scanning calorimetry and dynamic mechanical analysis, whereas transmission electron microscopy, melt rheology, and electrical conductivity were used to study the graphene dispersion. A decrease in heat capacity changes, ΔC p, of PET in nanocomposites at the glass transition temperature, T g, without T g change suggests that a rigid amorphous fraction (RAF) of PET was formed at the PET/graphene interface. The stiffening effect of graphene below 1 wt % loading is quite small in the glassy state region and independent of the A f of graphene. Above 2 wt %, graphene forms a mechanical percolation network with the RAF of PET and the PET chains are geometrically restricted by the incorporation of graphene with a high A f, resulting in an unexpectedly higher modulus of nanocomposites both below and above T g.

[Improvement of outcomes by primary treatment for temporomandibular disorders].

The aim of this study was to survey the current state of the temporomandibular joint disorder treatment in our clinic and to confirm the therapeutic outcomes. The subjects in this study were recruited from among the patients with temporomandibular disorders who attended the Temporomandibular Disorder Special Clinic, Department of Oral Surgery, Hitachi Yokohama Hospital during one year period from February 2007 to January 2008. A total of 100 consecutive outpatients diagnosed with temporomandibular disorders were selected for the study. Pain intensity and the degree to which daily function was limited before and after treatment were evaluated using the Visual Analogue Scale (VAS). The Beck Depression Inventory-II (BDI-II) score was evaluated simultaneously, and the correlation with changes in symptom was evaluated. The median (25th, 75th percentiles) of pain intensity (VAS value) before treated was 45 (25.0, 65.0) and the degree of limitation of daily function (VAS value) was 15 (0.0, 50.0). The median (25th, 75th percentiles) of pain intensity at 4 weeks after was 10 (0.0, 30.0), and significantly lower than that before treatment (p = 0.000). The degree of limitation of daily function was 0 (0.0, 10.0), also significantly lower than that before treatment (p = 0.000). The BDI-II score decreased from 8 (2.0, 11.8) before treatment to 5 (2.0, 11.0, p = 0.024) and showed no significant correlation with the improvement in outcomes by primary treatment for temporomandibular disorders.

Clinical evaluation of the temporomandibular joint following orthognathic surgery--multiple logistic regression analysis.

This study compares temporomandibular joint dysfunction (TMD) symptoms before and after bilateral sagittal split ramus osteotomy, and identifies predictive factors for the postoperative TMD symptoms by assessing the adjusted odds ratio using multiple logistic regression analysis. A consecutive series of 37 cases treated only with bilateral sagittal split ramus osteotomy were evaluated. New postoperative TMD symptoms appeared in 9 cases, preoperative TMD symptoms disappeared in 6 cases, and TMD symptoms were unchanged in 5 cases. The median period until the interincisal opening range attained 40 mm was 5 months (range, from 2 to 15 months). Age was a positive factor in patients with postoperative TMD symptoms, with an odds ratio of 1.43 (95 percent confidence interval, from 1.05 to 1.93). In addition, the maximum value of the bilateral setback distance of more than 9 mm was a positive factor of 6.95 (95 percent confidence interval, from 1.06 to 45.42). We concluded that surgical correction in skeletal malocclusion may affect temporomandibular joint dysfunction symptoms.

Clinical and magnetic resonance imaging study of unilateral sideways disc displacements of the temporomandibular joint.

The aim of our study was to find symptomatic diagnostic factors for sideways displacement of the temporomandibular joint disc, compared with anterior or rotational disc displacement. A consecutive series of 2310 temporomandibular joints were examined with MRI to define the clinical signs and symptoms particularly related to sideways disc displacement compared to anterior disc displacement with logistic regression model. Bone change of the mandibular condyle and age were negatively related factors in differentiating cases with lateral disc displacement from anterior disc displacement without reduction. Range of mouth opening (over 40 mm) was a significant predictor (odds ratio 4.5865 for lateral disc displacement). This study suggested the wide opening of the mouth to become the predictor for the lateral disc displacement among the cases suspected to have disc displacement without reduction.

[Postoperative evaluation of surgically treated cases with temporary silicone implant in temporomandibular joint].

We have carried out temporary silicone implants after diskectomies or arthroplasties in temporomandibular joint surgeries to avoid postoperative adhesion and to maintain articular space. We evaluated 19 joints in 15 patients who had received dacron-reinforced silicone implant after silicone sheet removal through follow-up for at least 6 months. The cases included temporomandibular joint disorder (10 joints in 9 patients), psoriatic arthritis (2 joints in 1 patient), ankylosis (4 joints in 3 patients) and synovial chondromatosis (2 joints in 2 patients). On the basis of the criteria of temporomandibular dysfunction for the results, they were classified as bad (4 patients). It is thought that factors other than the implant are related to the bad results in the postoperative evaluation. In this study, lymphadenopathy induced by exfoliated silicone debris could not be confirmed. The temporary silicone implant in the temporomandibular joint was thought to be useful.

Biotin-containing phospholipid vesicle layer formed on self-assembled monolayer of a saccharide-terminated alkyl disulfide for surface plasmon resonance biosensing.

We describe a technique to form a biotin-containing phospholipid vesicle layer on a self-assembled monolayer (SAM) deposited on a gold surface to immobilize biotinylated receptor proteins for a surface plasmon resonance (SPR) biosensor. The adsorption of vesicle of 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) was examined by SPR on the SAMs of dithiobis(1-deoxy-glucitol-1-carbamoyl pentane) (DDGP), 11-mercaptoundecanoic acid, 11-mercaptoundecanol, 11-amino-1-undecanethiol, and 12-mercaptododecane, and it was found that the DOPC vesicle rapidly adsorbed on the DDGP SAM to achieve the highest coverage of the surface. By quartz crystal microbalance with dissipation monitoring (QCM-D), the DOPC layer formed on the DDGP SAM was shown to be a vesicle layer, in which intact DOPC vesicles physisorbed on the SAM surface. To immobilize a biotinylated receptor protein, one of three biotinylated phospholipids, 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine-N-(biotinyl) (biotin-DOPE), N-((6-(biotinoyl)amino)hexanoyl)-1,2-dihexadecanoyl-sn-glycero-3-phosphoethanolamine (biotin-X-DHPE) and N-(biotinoyl)-1,2-dihexadecanoyl-sn-glycero-3-phosphoethanolamine (biotin-DHPE), was mixed with DOPC to form a biotin-containing vesicle layer on the DDGP SAM. A comparative binding study of NeutrAvidin and the biotin-containing vesicle layers showed that the use of biotin-X-DHPE achieved the most rapid immobilization of NeutrAvidin on the vesicle layer at the highest surface density. Furthermore, biotinylated protein A, as a receptor protein, could be immobilized through NeutrAvidin on the vesicle layer containing DOPC and biotin-X-DHPE, and its reaction with immunoglobulin G, as an analyte, was successfully observed by SPR. The results demonstrate that the biotin-containing vesicle layer on the DDGP SAM must be a useful component for SPR biosensor surfaces.

Hybrid normal-reverse prism coupler for light-emitting diode backlight systems.

For the first time to our knowledge, a hybrid normal-reverse prism coupler was formed on the bottom surface of a light guide in a LED backlight system to achieve a thin, lightweight, LED backlight system. The hybrid prism coupler (HPC) simultaneously exhibits two functions: extraction of guided light from the light guide and focusing the radiated light from the light guide, corresponding to the optical functions of the prism and diffusive sheets used in conventional LED backlight systems. Therefore, using a HPC eliminates the prism and diffusive sheets that have been indispensable optical elements in conventional LED backlight systems, which consequently reduces the thickness of the LED backlight system by 40% compared with conventional systems.

Grafting of poly(ethylene glycol) onto poly(acrylic acid)-coated glass for a protein-resistant surface.

The surface of solid glass supports for samples in optical microscopy and for biosensors needs to be protein-resistant. A coating of a poly(ethylene glycol) monomethyl ether (mPEG) on the surface of the glass is one promising method for preventing the nonspecific adsorption of proteins. In this study, we have developed a novel technique for achieving an optimal coverage of a glass surface with mPEG to prevent protein adhesion. A clean glass substrate previously treated with (3-aminopropyl)dimethylethoxysilane (APDMES) was treated sequentially with poly(acrylic acid) and subsequently a primary amine derivative of mPEG in the presence of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide. The resultant glass surface was demonstrated to be highly protein-resistant, and the adsorption of bovine serum albumin decreased to only a few percentage points of that on a glass surface treated with APDMES alone. Furthermore, to extend the present method, we also prepared a glass substrate on which biotinylated poly(ethylene glycol) was cografted with mPEG, and biotinylated myosin subfragment-1 (biotin-S1) was subsequently immobilized on this substrate by biotin/avidin chemistry. Actin filaments were observed to glide on the biotin-S1-coated glass surface in the presence of ATP, and thus, the method is capable of immobilizing the protein specifically without any loss in its biological function.