Hybrid Metallic Foam with Superior Elasticity, High Electrical Conductivity, and Pressure Sensitivity.

Growing interest has been received in metallic foams for their combined features of metals and porous structures. Coating metals on polymers have been the most prevalent method to fabricate hybrid metallic foams to inherit both the merits of metals and the mechanical flexibility of polymers. However, direct coating metals on foams is challenging and requires tedious synthesis, such as electrolysis and chemical reduction. This work reported a facile strategy to build hybrid metallic foams via in situ foaming of liquid metals (LM) and polyurethane. The fluidity and incompatibility of LM with porous polyurethane allow the coating of LM on polymers. LM-Foams exhibit high electrical conductivity (3.9 × 104 S/m), low density (ρ < 1 g/cm3), phenomenal elasticity (recover at 95% strain), and excellent mechanical stability (stable with 1000 compressive cycles). Interestingly, the ease of deformation for fluidic fillers in elastic polyurethane generates additional resistive change under pressure, showing unique sensory behaviors which were not observed in conventional conductive foams, such as high response sensitivity (gauge factor >25), short response time (202 ms), and outstanding electrical stability. The nonuniform size distribution of pores leads LM-Foams to show unusual position-dependent sensitivity, enabling advanced applications as password pads and electrical protection foams.

Early Experience of Full-Endoscopic Interlaminar Discectomy for Adolescent Lumbar Disc Herniation with Sciatic Scoliosis.

BACKGROUND: Full-endoscopic interlaminar discectomy (FEID) has achieved satisfactory outcome in adolescent lumbar disc herniation (ALDH). Sciatic scoliosis is found to be a common presentation in ALDH. However, few reports are focused on the influences of sciatic scoliosis on ALDH and the prognosis of sciatic scoliosis after FEID. OBJECTIVE: This study aims to evaluate the clinical and radiological results of FEID in the treatment of ALDH with sciatic scoliosis and to identify the effects of sciatic scoliosis on complication and recurrence. STUDY DESIGN: A retrospective study. SETTING: An inpatient surgery center. METHODS: A series of cases of patients under age 20 with single-level ALDH that underwent FEID between January 2010 and December 2014 were retrospectively analyzed. The patients were divided into 2 groups according to if they had scoliosis or not. Clinical outcomes were evaluated using a visual analog scale (VAS) for low back and leg pain, Oswestry Disability Index (ODI) for the functional assessment, and modified Macnab criteria for the patient satisfaction. Radiological parameters of the scoliosis group such as Cobb angle, CVSL-max, and CVSL-C7 were statistically analyzed. RESULTS: No significant differences were found between both groups in terms of the mean operative time, the mean length of hospital stay, complications, and recurrences (P > 0.05). VAS and ODI scores were significantly improved in both groups (P < 0.05). However, there were no statistically significant differences between the 2 groups in VAS, ODI, and modified MacNab criteria (P > 0.05). For the scoliosis group, significant improvements were observed in the postoperative sagittal and coronal alignment parameters (P < 0.05). LIMITATIONS: This was a retrospective study with a relatively small sample size. Additionally, the length of follow-up was short. CONCLUSIONS: The application of FEID in the treatment of ALDH could achieve satisfactory clinical and radiological outcomes. Sciatic scoliosis was corrected spontaneously without increasing the risk of complication and recurrence. KEY WORDS: Adolescent lumbar disc herniation, full-endoscopic interlaminar discectomy, sciatic scoliosis, recurrence.

Photochromic Inorganic/Organic Thermoplastic Elastomers.

Photochromic materials are an important class of "smart materials" and are broadly utilized in technological devices. However, most photochromic materials reported so far are composed of inorganic compounds that are challenging to process and suffer from poor mechanical performance, severely limiting their applications in various markets. In this paper, inorganic photochromic tungsten trioxide (WO3 ) nanocrystals are conveniently grafted with polymers to hurdle the deficiency in processability and mechanical properties. This new type of photochromic material can be thermally processed into desired geometries like disks and dog-bone specimens. Fully reversible photochromic response under UV light is also achieved for WO3 -graft polymers, exhibiting tunable response rate, outperforming the pristine WO3 nanocrystals. Notably, the resulted graft polymers show extraordinary mechanical performance with excellent ductility (≈800% breaking strain) and relatively high breaking strength (≈2 MPa). These discoveries elucidate an effective pathway to design smart inorganic/organic hybrid thermoplastic elastomers endowed with outstanding photochromic and mechanical properties as well as exceptional processability.

Toughening Glassy Poly(lactide) with Block Copolymer Micelles.

Poly(lactide) (PLA), a compostable bioderived polyester, can be produced at a cost and scale that makes it an attractive replacement for nondegradable petroleum-derived thermoplastics. However, pristine PLA is brittle and unsuitable for use in applications where high impact strength and ductility are required. In this work we demonstrate that poly(l-lactide) (PLLA) in the glassy state can be toughened significantly via addition of an amphiphilic diblock polymer. Notably, a PLLA blend containing only 5 wt% poly(ethylene oxide)-b-poly(butylene oxide) (PEO-PBO) exhibited tensile toughness and notched Izod impact strength over an order of magnitude higher than neat amorphous PLLA without a significant reduction in transparency or elastic modulus. For a series of PLLA blends containing PEO-PBO of fixed composition (∼70% volume fraction PBO), the toughness was inversely related to the molar mass of the added modifier with the highest toughness observed for the blend containing the smallest diblock (∼7 kg/mol). Interestingly, at fixed composition and molar mass poly(l-lactide)-b-poly(butylene oxide) (PLLA-PBO) exhibited a substantial but reduced toughening efficiency compared to PEO-PBO. We attribute this difference to a change in the solubility parameter of the amphiphilc block. Using TEM, we show that the greatest toughening is observed when the diblock modifier forms small cylindrical micelles that are well dispersed in the PLLA matrix. This morphology is facilitated by a negative Flory-Huggins interaction parameter (χ) between PEO and PLLA. These insights suggest a new and versatile strategy for the facile and efficient toughening of brittle thermoplastics.

Tough and Sustainable Graft Block Copolymer Thermoplastics.

Fully sustainable poly[HPMC-g-(PMVL-b-PLLA)] graft block copolymer thermoplastics were prepared from hydroxypropyl methylcellulose (HPMC), ß-methyl-δ-valerolactone (MVL), and l-lactide (LLA) using a facile two-step sequential addition approach. In these materials, rubbery PMVL functions as a bridge between the semirigid HPMC backbone and the hard PLLA end blocks. This specific arrangement facilitates PLLA crystallization, which induces microphase separation and physical cross-linking. By changing the backbone molar mass or side chain composition, these thermoplastic materials can be easily tailored to access either plastic or elastomeric behavior. Moreover, the graft block architecture can be utilized to overcome the processing limitations inherent to linear block polymers. Good control over molar mass and composition enables the deliberate design of HPMC-g-(PMVL-b-PLLA) samples that are incapable of microphase separation in the melt state. These materials are characterized by relatively low zero shear viscosities in the melt state, an indication of easy processability. The simple and scalable synthetic procedure, use of inexpensive and renewable precursors, and exceptional rheological and mechanical properties make HPMC-g-(PMVL-b-PLLA) polymers attractive for a broad range of applications.