Interfacial Area Ratio Research Articles

Bonding to CAD-CAM Composites: An Interfacial Fracture Toughness Approach

The objective of this study was to evaluate the interfacial fracture toughness (IFT) of composite cement with dispersed filler (DF) versus polymer-infiltrated ceramic network (PICN) computer-aided design and computer-aided manufacturing (CAD-CAM) composite blocks after 2 different surface pretreatments using the notchless triangular prism (NTP) test. Two DFs (Cerasmart [CRT] and Lava Ultimate [LVA]), 2 PICNs (Enamic [ENA] and experimental PICN [EXP]), and e.max CAD lithium disilicate glass-ceramic (EMX, control) prism samples were bonded to their counterparts with Variolink Esthetic DC composite cement after either hydrofluoric acid etching (HF) or gritblasting (GR). Both procedures were followed by silanization. All samples (n = 30 per group) were thermocycled (10,000 cycles) and tested for their IFT in a water bath at 36°C. Moreover, representative samples from each group were subjected to a developed interfacial area ratio (Sdr) measurement by profilometry and scanning electron microscopy (SEM) characterization. EXP-HF gave the highest IFT (1.85 ± 0.39 MPa·m1/2), followed by EMX-HF and ENA-HF, while CRT-HF gave the lowest (0.15 ± 0.22 MPa·m1/2). PICNs gave significantly better results with HF, and DF showed better results with GR. A 2-way analysis of variance indicated that there were significantly higher IFT and Sdr for PICNs than for DF. A positive correlation (r² = 0.872) was found between IFT and Sdr. SEM characterization showed the specific microstructure of the surface of etched PICNs, indicating the presence of a retentive polymer-based honeycomb structure. Etching of the typical double-network microstructure of PICNs causes an important increase in the Sdr and IFT, while DF should be gritblasted. DF exhibited significantly lower Sdr and IFT values than PICNs. The present results show the important influence of the material class and surface texture, and consequently the micromechanical bond, on the adhesive interface performance of CAD-CAM composites.

Heat and mass transfer in a copper oxy-chloride spray reactor for thermochemical hydrogen production

A new predictive model is developed in this paper to analyze the height of the reactor for continuous production of copper oxy-chloride in the thermochemical Cu–Cl cycle for hydrogen production. The volumetric phase fraction is used to develop an energy balance and integrated spatially to determine the inlet temperature of nitrogen and steam mixtures for continuous production of copper oxy-chloride. The effects of the ratio of mixing power to mass of the suspended particle, the ratio of interfacial surface area of the gas film to the volume of liquid, and diameter of the steam/nitrogen bubble in the reactor, on the height of the reactor are reported for a production capacity of 3 kg of hydrogen per day. Results indicate that a smaller ratio of interfacial surface area to volume of liquid significantly reduces the height of the reactor.

Effects of Surface Treatments on the Bond Strength Between Resin Cement and a New Zirconia-reinforced Lithium Silicate Ceramic

This study evaluated the effects of surface treatments on the bond strength between the new zirconia-reinforced lithium silicate ceramic (ZLS) and resin cement. VITA Suprinity blocks were crystallized according to the manufacturer's instructions and randomly assigned to six groups (N=36; n=6), according to the surface treatment to be performed and aging conditions: HF20, 10% hydrofluoric acid for 20 seconds, baseline (control); HF20tc, 10% hydrofluoric acid for 20 seconds, aging; HF40, 10% hydrofluoric acid for 40 seconds, baseline; HF40tc, 10% hydrofluoric acid for 40 seconds, aging; CJ, CoJet sandblasting (25 seconds, 2.5 bar, 15-mm distance), baseline; and CJtc, CoJet sandblasting (25 seconds, 2.5 bar, 15-mm distance), aging. All specimens were silanized (Monobond S) and cemented with Panavia F to newly polymerized Z250 resin blocks. After specimens were immersed for 24 hours in distilled water at 37° C, 1-mm(2) cross-section microbars were obtained by means of a cutting machine under constant cooling. Baseline groups were immediately tested, whereas "tc" groups were used to analyze the effect of aging on bond strength (10,000 thermal cycles, 5/55°C, 30-second bath). The microtensile bond strength test was performed with a universal testing machine (0.5 mm/min), and bond strength (MPa) was calculated when the load-to-failure (N) was divided by the adhesive area (mm(2)). We also evaluated the surface roughness (Sa, average roughness; Str, texture aspect ratio; Sdr, developed interfacial area ratio) and the contact angle resulting from the treatments. Data were statistically analyzed by one- or two-way analysis of variance and Tukey's test (all α=5%). The failure mode of each specimen was evaluated by stereomicroscopy, and representative specimens were analyzed by scanning electron microscopy. The microtensile bond strength was affected by the surface conditioning (p<0.0001), storage condition (p<0.0001), and the interaction between them (p=0.0012). The adhesion for HF etching was stable, whereas for CJ, aging significantly damaged the adhesion. Most failures were predominantly adhesive between ceramic and cement (52.6%). The roughness of the treated samples was higher compared with that of polished specimens for the three evaluated parameters (Sa, Str, and Sdr; all p<0.0001). Contact angle was also influenced by treatments (p<0.0001), with the CJ group showing values similar to those of control specimens. It can be concluded that the three surface treatment techniques present favorable immediate results, but silica coating was not effective in maintaining the bond strength over the long term.

Modeling the Release of Nitrogen from Controlled-Release Fertilizer with Imperfect Coating in Soils and Water

Urea is vulnerable to losses from volatilization or leaching when applied to soils. This study proposes a porous model that couples the interfacial area ratio (IAR) equation for the diffusion of nitrogen with mass transport equation in porous medium (soil). The model presents the release of a single granule with an imperfect coating thickness in different environments. The model is validated with experiments in water and soil environments. In addition, it is compared to our previous model and shows an enhancement in its predictive ability because the imperfection of the coating layer has been integrated in the model. On the basis of the proposed model, the influence of coating variation and soil types also are investigated. In general, simulation results suggest that the coating layer imperfection leads to earlier and faster nitrogen release than an ideal one. Also, nitrogen release in soil depends on soil characteristics such as surface area, particle size, and density. The comparison with experimental o...

Three-Dimensional Nanostructures with Biocidal Activity Created on a Siloxane-Containing Copolyimide Film

Surface morphological characteristics of a copolyimide film prepared from a fluorine-based dianhydride combined with an aliphatic siloxane-based diamine and an aromatic containing ether linkages one, were studied before and after oxigen plasma treatment using atomic force microscopy (AFM). The three-dimensional texture parameters calculated from the AFM data have highlighted a more pronounced surface morphology (higher average roughness and developed interfacial area ratio), improved bearing properties and no predominant orientation, as the plasma exposure time was increased from 6 to 10 minutes, using the same power (40 W). The reactive groups generated on the binding surface have facilitated the interaction with a biocidal agent, such as silver nitrate. This creates silver-containing nanoparticles, of about 120-150 nm, uniformly distributed on the copolymer surface, with a density of 10±2 particles/μm2. The functionalization with the biocidal agent of the flourinated copolyimide surface was conducted for testing its antimicrobial properties, namely the inhibition/destruction of Escherichia coli bacterium.

An in vitro study on the effect of an oscillating stripping method on enamel roughness.

BackgroundThe aim of the present study was to assess the changes in enamel roughness parameters before and after stripping with an oscillating diamond strip system.MethodsSound premolars extracted for orthodontic reasons were embedded up to their cervical area in a polyvinylsiloxane putty, creating four groups of four teeth with three interproximal areas each (mesial/distal). The same regions of interproximal enamel surfaces were studied by 3D optical interferometric profilometry before and after stripping with the Ortho-Strips system (Intensiv Dental SA, Montagnola, Switzerland) (n teeth = 16, n contact points = 12, n sites measured = 24). The roughness parameters tested were the amplitude parameters Sa and Sz, the hybrid parameter Sdr, and the functional parameters Sci and Svi. The parameter differences (ΔSa, ΔSz, ΔSdr, ΔSci, ΔSvi) were calculated per region and statistically analyzed by one-sample Mann-Whitney rank sum test (a = 0.05).ResultsHigh statistically significant differences were found in ΔSa, ΔSz, and ΔSvi median values (0.453, 3.870, and 0.040 μm, respectively); a significant difference in ΔSdr median value (1.514%); and no statistically significant difference in ΔSci (0.110 median value).ConclusionsUnder the conditions of the present study, the Ortho-Strips system seems to significantly increase the amplitude parameters Sa and Sz; the hybrid parameter Sdr, associated with the developed interfacial area ratio; and the functional parameter Svi, which depicts the volume of the deepest valleys. Under the conditions of the present study, the Ortho-Strips seems to significantly increase four of five measured roughness parameters.

Anisotropy and roughness of the solid-liquid interface of BCC Fe.

Melting point T m and kinetic coefficient μ (a proportional constant between the interfacial velocity ν and undercooling ΔT), along with the structural roughness of the solid-liquid interface for body centered cubic (BCC) Fe were calculated by molecular dynamics (MD) simulation. All simulations applied the Sutton-Chen potential, and adopted average bond orientational order (ABOO) parameters together with Voronoi polyhedron method to characterize atomic structure and calculate atomic volume. Anisotropy of T m was found through about 20~40K decreasing from [100] to [110] and continuously to [111]. Anisotropy of μ with three low index orientations was found as: μ s,[100] > > μ s,[110] > μ s,[111] for solidifying process and μ m,[100] > > μ m,[111] > μ m,[110] for melting process. Slight asymmetry between melting and solidifying was discovered from that the ratios of μ m/μ s are all slightly larger than 1. To explain these, interfacial roughness R int and area ratio S/S 0 (ratio of realistic interfacial area S and the ideal flat cross-sectional area S 0) were defined to verify the anisotropy of interfacial roughness under different supercoolings/superheatings. The results indicated interfacial roughness anisotropies were approximately [100] > [111] > [110]; the interface in melting process is rougher than that in solidifying process; asymmetry of interfacial roughness was larger when temperature deviation ΔT was larger. Anisotropy and asymmetry of interfacial roughness fitted the case of kinetic coefficient μ very well, which could give some explanations to the anisotropies of T m and μ.

Mesoscale elucidation of the influence of mixing sequence in electrode processing.

Mixing sequence during electrode processing affects the internal microstructure and resultant performance of a lithium-ion battery. In order to fundamentally understand the microstructure evolution during electrode processing, a mesoscale model is presented, which investigates the influence of mixing sequence for different evaporation conditions. Our results demonstrate that a stepwise mixing sequence can produce larger conductive interfacial area ratios than that via a one-step mixing sequence. Small-sized cubical nanoparticles are beneficial for achieving a high conductive interfacial area ratio when a stepwise mixing sequence is employed. Two variants of multistep mixing have been investigated with constant temperature and linearly increasing temperature conditions. It is found that the temperature condition does not significantly affect the conductive interfacial area ratio. The homogeneity of binder distribution in the electrode is also studied, which plays an important role along with the solvent evaporation condition. This study suggests that an appropriate combination of mixing sequence and active particle size and morphology plays a critical role in the formation of electrode microstructures with improved performance.

Surface properties correlated with the human gingival fibroblasts attachment on various materials for implant abutments: A multiple regression analysis

Objectives. To reveal the suitable surface condition of an implant abutment for fibroblast attachment, the correlation between the surface characteristics of various materials and the human gingival fibroblast (HGF-1) attachment to the surfaces were analyzed. Methods. Six kinds of surfaces comprised of machined titanium alloy (SM), machined Co-Cr-Mo alloy (CCM), titanium nitride coated titanium alloy (TiN), anodized titanium alloy (AO), composite resin coating on titanium alloy (R) and zirconia (Zr) were used. The measured surface parameters were Sa, Sq, Sz, Sdr, Sdq, Sal, Str and water contact angle (WCA). The HGF-1 cell attachment was investigated and the correlations were analyzed using a multiple regression analysis. Results. The HGF-1 cell attachment was greater in the SM, TiN and Zr groups than the other groups and smallest in the CCM group (p = 0.0096). From the multiple regression analysis, the HGF-1 cell attachment was significantly correlated with Sdr, Sdq and WCA. When the R group was excluded, only WCA showed significant correlation with the fibroblast attachment. Conclusions. Within the limitations of this study, the cell attachment of human gingival fibroblasts was correlated with WCA, developed interfacial area ratio and surface slope. When the surfaces with Sa values of ∼ 0.2 μm or less were concerned, only WCA showed a correlation in a third order manner.

Human Gingival Fibroblast (HGF-1) Attachment and Proliferation on Several Abutment Materials with Various Colors

An implant abutment should be soft tissue-compatible and resistant to plaque accumulation, and it is preferable for an implant abutment to have color harmony with the surrounding tissues. This study aimed to compare the in vitro fibroblast cell attachment and proliferation on several abutment materials of different colors. A total of 240 specimens in 6 experimental groups were used: titanium alloy (SM [smooth machined]; gray), cobalt-chrome-molybdenum alloy (CCM; gray), titanium nitride-coated titanium (TiN; yellow), anodic-oxidized titanium (AO; dark pink), composite resin-coated titanium (R; white), and zirconia (Zr; white). The culture plate surface was employed as a control (C). The surface roughness (Sa), developed interfacial area ratio (Sdr), and water contact angle (WCA) were measured. The human gingival fibroblast (HGF-1) attachment and proliferation at the third and seventh days were observed. Sa values of all experimental groups were < 0.5 μm. Sdr values were between 5% and 8%, except for the Zr group (0.06%). WCA of all groups was greater than 40 degrees. More HGF-1 cells attached on the surfaces of the SM, TiN, and Zr groups than the C group, and the least number of cells were observed on the CCM group (P < .001). On the third day of proliferation, the C group showed significantly greater proliferation than all experimental groups (P < .001). On the seventh day of proliferation, the TiN, AO, Zr, and C groups exhibited twice the number of cells compared to the rest of the groups (P < .001). Within the limitations of this study, zirconia abutments would be the best choice in the anterior region. Titanium nitride-coated titanium alloy abutments or anodic-oxidized titanium alloy abutments might also be good choices in areas of esthetic challenge or under high occlusal loads.

Further study of grain boundary fracture in the breakage of single multiphase particles using X-ray microtomography procedures

The present work aims to verify the 3D quantitative analysis of grain boundary fracture in the breakage of single multiphase particles using X-ray microtomography. The breakage of single multiphase copper ore particles (6mm cubic particles) by slow compression was examined. From XMT reconstructed images using the Marching Cube method, interfacial areas between copper mineral grains and host rock were determined for both parent particles and progeny particles. In this way, the specific interfacial area ratio was calculated as a metric for grain boundary fracture. Preferential grain boundary fracture only occurs at low energy dissipation rates and the current results confirm initial results for 3mm cubes published previously by Garcia et al. (2009).

Response of osteoblast-like cells to zirconia with different surface topography

The objective of this study was to clarify the effect of surface topography on osteoblast-like cell behavior on yttria stabilized tetragonal zirconia polycrystals (TZP). Mirror-polished; blasted with 50- or 150-µm alumina (SB50 and SB150); and SB150 acid-etched with hydrofluoric acid (SB150E) were prepared on TZP. Initial attachment, proliferation and differentiation of MC3T3-E1 were evaluated. The scanning electron microscopy and Sdr (developed interfacial area ratio) values indicated that both micro- and nano-topographies produced on the SB150E surfaces. Although no clear differences were observed in initial cell attachment among specimens, the proliferation rate and expression of ALP activity on the SB150E specimens was significantly higher than that on the other specimens. These results indicate that the creation of micro- and nano-topographies on TZP by surface treatment offers a promising method of enhancing the proliferation and differentiation of MC3T3-E1 cells.

The Effect of Aperture Size on Gigaseal Formation

Patch clamping, the gold standard for ion channel studies, is entirely dependent on formation of a high resistance seal between cell membrane and patching site,known as gigaseal. As this process is laborious and time consuming, there have been many attempts to develop automated high throughput chip-based patch clamping devices. In spite of recent advances, these devices still cannot form gigaseals relying instead on less tight seals that impede their ability to measure the pA ionic currents passing through single ion channels. Progress is presently limited due to a lack of understanding of the physical and chemical mechanisms underlying gigaseal formation. In all forms of patch clamping access to the cell is achieved via a small aperture. Here, we systematically examine the influence of aperture size, micropipette rim morphology, and surface roughness on gigaseal formation in conventional patch clamping using micro/nanofabrication and modelling techniques. Our results show that smaller aperture sizes lead to improved seal formation within a range of x-y. For aperture sizes out of this range, either bigger or smaller, gigaseal formation is very difficult if not impossible. While in the literature the surface quality of patching sites is only described by average surface roughness, this research reveals that parameters such as: developed interfacial area ratio, valley void volume of the surface, ratio of core void volume to core material volume, and maximum peak to valley distance play more important roles in seal formation. Furthermore,these parameters are size dependent; as a result glass micropipettes with smaller aperture sizes are flatter and have lower water retentionability resulting in better seals. Results of this work support the practical knowledge that pipettes having smaller apertures form better seals.

Analysis of two-phase contacting in a rotating spiral channel

The separation of one component from a multicomponent fluid solution is commonly achieved by bringing the solution into contact with a second immiscible phase, as in liquid–liquid or gas–liquid contactors. Counter-current flow of the phases allows high purity separations and existing approaches typically force one of the phases to disperse into the other, producing the close contact necessary for the solute species to be distributed by diffusion throughout the volume of each phase. This phase mixing leaves the contacting strongly dependent on fluid and interface mechanical properties. Thus an approach that suits one phase and solute system will not necessarily suit others. In addition, it is then necessary to separate the dispersed phase which can be a major drawback of the operation sometimes posing substantial difficulties in easily emulsified liquid–liquid systems or in easily foamed gas–liquid systems. A new approach, which has recently been demonstrated experimentally for microchannels, uses a rotating spiral channel to allow controlled contacting giving a very high ratio of interfacial surface area to fluid volume but avoids phase mixing. Its application to larger channels, up to millimetres in size, is considered here. The two phases are forced to flow side by side in parallel layers along the narrow spiral channel. Selection of spiral parameters, rotation rate and pressure gradient along the channel controls the flow rate ratio of the phases and the relative thickness of the phase layers. This allows adjustment to reach the optimum mass transfer (limited strongly neither by one phase nor the other) and adaptation to phase and solute systems having widely differing fluid viscosities, densities, solute diffusivities and interface equilibria. With appropriate control over these parameters, a single device is, in principle, capable of application to a wide range of separation requirements. This rotating spiral contacting is, however, a new technology and remains to be investigated and tested in detail. The present work develops a model yielding both quantitative prediction of flow and mass transfer in the contacting channel and a framework for determining suitable designs, operating conditions and mass transfer performance for liquid–liquid and gas–liquid operations.

Surface properties of glass micropipettes and their effect on biological studies

In this paper, an investigation on surface properties of glass micropipettes and their effect on biological applications is reported. Pipettes were pulled under different pulling conditions and the effect of each pulling parameter was analyzed. SEM stereoscopic technique was used to reveal the surface roughness properties of pipette tip and pipette inner wall in 3D. More than 20 pipettes were reconstructed. Pipette heads were split open using focused ion beam (FIB) milling for access to the inner walls. It is found that surface roughness parameters are strongly related on the tip size. Bigger pipettes have higher average surface roughness and lower developed interfacial area ratio. Furthermore, the autocorrelation of roughness model of the inner surface shows that the inner surface does not have any tendency of orientation and is not affected by pulling direction. To investigate the effect of surface roughness properties on biological applications, patch-clamping tests were carried out by conventional and FIB-polished pipettes. The results of the experiments show that polished pipettes make significantly better seals. The results of this work are of important reference value for achieving pipettes with desired surface properties and can be used to explain biological phenomenon such as giga-seal formation.

Extension of Kozeny‐Carman Model for Estimating Unsaturated Hydraulic Conductivity

We present a predictive model for unsaturated hydraulic conductivity (K) which makes use of the interrelationship among capillary pressure (Pc), wetting phase saturation (Sw), and nonwetting–wetting phase interfacial area. The newly developed model is general so that any closed form Pc–Sw equation can be incorporated. In particular, we formulate Kozeny–Carman–Brooks–Corey (KCBC) and Kozeny–Carman–van Genuchten (KCVG) models by including, respectively, the closed‐form Brooks–Corey and van Genuchten Pc–Sw equations in the modified Kozeny–Carman (KC) model. For Sw ≈ Se, Se is effective saturation, the interfacial area based KCBC equation is identical to the geometrically (wetting phase hydraulic radius) based Brooks–Corey–Burdine (BCB) semi‐empirical model. The capillary pressure thermodynamics are used to describe the KCBC/KCVG relative permeability integrals as well as a variable tortuosity–connectivity, defined as the ratio of interfacial area for a soil sample to the interfacial area for the corresponding, idealized capillary bundle. The new model is tested for a database composed of 22 coarse‐textured and 24 fine‐textured samples. With the decoupling of the relative permeability integrals from the conventional Pc–Sw derived pore‐size distribution models, both KCBC and KCVG formulations provide a good agreement between measured and predicted K for the fine‐ as well as coarse‐textured sediments. The use of the conventional BCB and van Genuchten‐Mualem (VGM) models results in large deviations between measured and predicted K, and considerable bias. To the contrary, for the entire moisture regime, the use of the KCBC and KCVG models produces very little bias and results in a comparable agreement for KCBC and KCVG model predictions with K(θ) measurements. Overall, the modified KC model, with interfacial areas derived from the thermodynamics of Pc, provide an improved description of K(θ) measurements, compared with standard BCB and VGM models.

Macroscopic Behavior of Carbon Nanotube (CNT)-Reinforced Composite Accounting for Interface Cohesive Force

The large aspect ratio of interfacial area per unit volume at CNT/matrix interfaces may significantly influence the macroscopic behavior of CNT-reinforced composites. The property of interfaces is governed by the cohesive law, which is determined from both van der Waals forces and chemical covalent bonds. This nonlinear cohesive law is incorporated in the micromechanics model in the current work to study the mechanical behavior of CNT-reinforced composites. It is found that carbon nanotubes can improve the macroscopic behavior of the composite at small strain, but tend to weaken the composite at relatively large strain because of the interface softening behavior or debonding. The increase of interface adhesion caused by the creation of chemical covalent bonds may significantly improve the composite behavior at large strain.

The effect of surface treatment on the surface texture and contact angle of electrochemically deposited hydroxyapatite coating and on its interaction with bone-forming cells

This work demonstrates the effects of both surface preparation and surface post-treatment by exposure to electron beam on the surface texture, contact angle and the interaction with bone-forming cells of electrochemically deposited hydroxyapatite (HAp) coating. Both the surface texture and the contact angle of the ground titanium substrate changed as a result of either heat treatment following soaking in NaOH solution or soaking in H 2O 2 solution. Consequently, the shape of the current transients during potentiostatic deposition of HAp changed, and the resulting coatings exhibited different surface textures and contact angles. The developed interfacial area ratio Sdr and the core fluid retention index Sci were found more reliable than the mean roughness R a and the root-mean-square roughness Z rms in correlating the adhesion of the coating to the metal substrate and the cellular response with surface texture. The NaOH pretreatment provided the highest surface area and induced the highest cell attachment, even though the H 2O 2 treatment provided the highest hydrophilicity to the metal substrate. Electrodeposition at pH 6 was found preferable compared to electrodeposition at pH 4.2. The ability to modify the cellular response by exposure to unique electron-beam surface treatment was demonstrated. The very high hydrophilicity of the as-deposited HAp coating enhanced its bioactivity.

Titanium Dental Implant Surface Micromorphology Optimization

The purpose of this investigation was to create an acid-etched implant surface that is similar to that created by sandblasting combined with acid etching and to compare it with the surfaces of various commercially available screw-type implants. Titanium grade 5 disks were machined in preparation for acid etching. Tests were carried out using different acids and combinations of them with varying time exposures. All etched surfaces were scanned with an electron microscope, and digital images were created for visual evaluation and description of the surfaces. The etched surfaces were evaluated for surface morphology (combination of microroughness and waviness); the surface most like the sandblasted/acid-etched surface was best obtained with a combination of sulfuric and hydrochloric acids. The etched titanium disks were fixed in acrylic resin (2 were cut and polished and 2 were scored and fractured) and the surface profile was examined. In the second part of the investigation, 28 screw-shaped implants that were manufactured from commercially available titanium grade 5 were selected and divided into 2 groups: 3 implants were used as controls (machined surface), and 25 implants were processed using the preferred etching method determined in the first part of the investigation. Magnifications of 27, 200, and 2000 were used to analyze the first 2 consecutive crests of threads, flanks, and root of threads of each implant with the treated surface. A 3-dimensional optical interferometer was used to characterize the surface roughness of both control and test groups. Three screws were selected from each group and measured at 9 sites: 3 measurements each on the crest, root, and flank of the threads. To describe the surface roughness in numbers, the following parameters were used: the average height deviation (Sa), the developed interfacial area ratio (Sdr), the fastest decay autocorrelation length (Sal), and the density of summits (Sds). In addition, in a third experiment, the surfaces of 5 commercially available screw-type implants and the experimental ones were analyzed and compared. It was concluded that the new experimental acid-etched titanium surface had the features of a roughened titanium surface, with glossily microroughness and large waviness. In general, the experimental surface was significantly rougher than the selected commercially available implants and similar to a sandblasted/acid-etched surface (top Sa: 2.08 +/- 0.36 microm, Sdr: 1.34 +/- 0.3 microm, valleys: 1.16 +/- 0.1 microm and 0.68 +/- 0.1 microm, flanks: 2.24 +/- 0.8 microm and 1.27 +/- 0.1 microm, respectively).

Self-Assembly and Chain-Folding in Hybrid Coil−Coil−Cube Triblock Oligomers of Polyethylene-b-Poly(ethylene oxide)-b-Polyhedral Oligomeric Silsesquioxane

Self-assembly and chain-folding in well-defined oligomeric polyethylene-block-poly(ethylene oxide)-block-polyhedral oligomeric silsesquioxane (PE-b-PEO-b-POSS) triblock molecules were studied by small-angle X-ray scattering (SAXS), wide-angle X-ray diffraction (WAXD), and transmission electron microscopy (TEM). The triblock oligomers were synthesized by attaching two kinds of functional POSS molecules, namely, isocyanatopropyldimethylsilylisobutyl-POSS (Ib−POSS) and isocyanatopropyldimethylsilylcyclopentyl-POSS (Cp−POSS), to a hydroxyl-terminated PE-b-PEO-OH diblock oligomer (denoted as E39EO23) via urethane reactions. In these triblock oligomers, both PE and POSS were crystalline, whereas PEO became amorphous due to tethering of its both ends to other two blocks. In the crystalline state, PE chains tilted 32° from the lamellar normal, and both Ib−POSS and Cp−POSS molecules stacked into four-layer (ABCA) lamellar crystals, having the same trigonal (R3̄m) symmetry as in pure POSS crystals. Because the cross-sectional area for a PE chain in the PE crystals (0.216 nm2/chain) at the interface was much smaller than that for a POSS molecule in POSS crystals (1.136 nm2/molecule), the self-assembly and PE chain-folding were substantially affected by the sequence of PE and POSS crystallization when crystallizing from the melt. For example, PE crystallization induced the POSS crystallization in the bulk E39EO23−Ib−POSS, and thus extended-chain PE crystals were observed. The grains of crystalline lamellae again were small with often highly curved lamellar crystals. This could also be attributed to the unbalanced interfacial areas for POSS and PE blocks (the interfacial area ratio being 2.6 for interdigitated PE crystals, i.e., two PE chains per POSS molecule). For the E39EO23−Cp−POSS triblock oligomer, POSS molecules crystallized before PE crystallization, forming a well-defined lamellar structure. The preexisting POSS crystals confined the PE crystallization, and thus almost once-folded PE crystals were obtained. Because the interfacial area ratio between POSS and PE blocks decreased to 1.3, the crystalline lamellae were straight and their grains were relatively large. On the basis of this study, we conclude that confinement effect plays an important role on chain-folding of crystalline block oligomers, which in turn determines the unbalanced cross-sectional areas between chemically different blocks and finally dictates their final crystalline morphology.