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The Formation of Broadband Color Centers in PMMA by Femtosecond Laser Radiation
摘要： At present, organic materials modified by the laser irradiation are frequently used for the development and production of optical elements. Poly(methyl methacrylate) (PMMA) is one of the polymer materials which are most widely used in optics and optoelectronics. A broad transparency window and the ease of industrial processing are the main advantages of PMMA. Laser modification of PMMA allows creating color centers with radiation in a wide spectral range.
关键词： Poly(methyl methacrylate),color centers,laser modification
更新于2025-09-12 10:27:22
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Phase diagram of colloidal crystals of poly(methyl methacrylate) spheres in the exhaustively deionized dispersion
摘要： Phase diagram of colloidal crystals of poly(methyl methacrylate) (PMMA) spheres (100 to 300 nm in diameter) was measured precisely for the exhaustively deionized aqueous dispersion. Strong iridescent colors changed from bluish to reddish and metallic as sphere size increased at high sphere concentrations around 0.1 in volume fraction. Large single crystals, on the other hand, were recognized with the naked eyes at low sphere concentrations around 0.0005 to 0.001 especially for PMMA spheres smaller than 200 nm. The critical concentrations of melting (or crystallization), ?c of all the PMMA spheres examined were quite low between 0.00025 and 0.00060 in volume fraction. The ?c values were insensitive to kind (polystyrene, silica, and fluorine-containing spheres) and also to size (90~300 nm) of colloidal spheres. The ?c value of the deionized dispersion with the coexistence of the ion-exchange resins was lowest, and that without resins was tenfold large. Addition of sodium chloride increased the ?c values sharply. Extension of the electrical double layers forming around the colloidal spheres is most important to determine the ?c values.
关键词： Critical concentration of melting,Phase diagram,Colloidal crystal,Deionized dispersion,Poly(methyl methacrylate) spheres
更新于2025-09-10 09:29:36
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Biomaterials and Regenerative Medicine in Ophthalmology || An introduction to ophthalmic biomaterials and their role in tissue engineering and regenerative medicine
摘要： The ultimate goal of the research and development of materials (other than drugs) for applications in medicine, which we call biomaterials, has always been to emulate natural materials. Since the natural target for biomaterials, ie, our body’s tissues and organs, is exceedingly complex, it is not surprising that in many instances the laboratory-made materials cannot match in their performance the natural entities they are meant to augment or replace. This is obviously different from the development of materials for industrial applications, which usually perform better than their natural counterparts (if the latter exist), and also evolve relatively fast, unhindered by the biological constraints inherent to living systems. For too long, an acceptable end performance in the short term was the main requirement from a biomaterial, with little attention paid to changing its bulk and/or surface properties through the manipulation of composition and/or structure, in order to maximize the clinical outcome. Over the past six decades or so, however, the progress in bringing the properties and functionality of biomaterials close to those of their biological targets has been remarkable. While the previous statements are valid for the ophthalmic biomaterials too, their development has shown some particular features. The general developments in the field of biomaterials have customarily been gauged through the achievements in the branches of orthopaedic biomaterials and, to a lesser extent, biomaterials for cardiology or dentistry, while the progress of biomaterials for the eye has usually been ignored or seldom presented.
关键词： ophthalmic biomaterials,artificial cornea,poly(methyl methacrylate),contact lenses,hydrogels,cornea,regenerative medicine,tissue engineering
更新于2025-09-10 09:29:36
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Zero-Birefringence Composition and Orientation Birefringence of PMMA/PVB Blends
摘要： Blends of poly(methyl methacrylate) (PMMA) and poly(vinyl butyral) (PVB) exhibit zero-birefringence due to the compensation of negative birefringence of PMMA and positive birefringence of PVB, respectively. The zero-birefringence composition of drawn-quenched specimens was found to be quite different from that induced by deformation at room temperature. The zero-birefringence composition was calculated by the additivity of the orientation and/or distortion birefringence of the neat component polymers, which were evaluated by the curve fitting procedures of the relaxation birefringence and relaxation stress. The calculation results revealed that the birefringence of the drawn-quenched specimens is attributed to the orientation birefringence in the glassy state while that of the deformation at room temperature is attributed to both orientation and distortion birefringence at room temperature.
关键词： Poly(methyl methacrylate),Orientation,Poly(vinyl butyral),Birefringence,Blend
更新于2025-09-09 09:28:46
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Preparation and Properties of ZnO:Ce/Poly(methyl methacrylate) Nanocomposites via in situ Copolymerization
摘要： Novel inorganic/polymer nanocomposites were prepared by using in situ copolymerization of the modified inorganic nano-ZnO:Ce and methyl methacrylate. X-ray diffraction and SEM were employed to characterize the structure and morphology. Tensile test and TGA show that the incorporation of ZnO:Ce nanoparticles into poly(methyl methacrylate) matrix can significantly improve the mechanical and thermal properties of the composite.
关键词： Nanocomposites,ZnO:Ce,Properties,Poly(methyl methacrylate)
更新于2025-09-09 09:28:46
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Direct formation of gold nanorods on surfaces using polymer-immobilised gold seeds
摘要： Herein, we present the formation of gold nanorods (GNRs) on novel gold–poly(methyl methacrylate) (Au–PMMA) nanocomposite substrates with unprecedented growth control through the polymer molecular weight (Mw) and gold-salt-to-polymer weight ratio. For the first time, GNRs have been produced by seed-mediated direct growth on surfaces that were pre-coated with polymer-immobilised gold seeds. A Au–PMMA nanocomposite formed by UV photoreduction has been used as the gold seed. The influence of polymer Mw and gold concentration on the formation of GNRs has been investigated and discussed. The polymer nanocomposite formed with a lower Mw PMMA and 20 wt % gold salt provides a suitable medium for growing well-dispersed GNRs. In this sample, the average dimension of produced GNRs is 200 nm in length with aspect ratios up to 10 and a distribution of GNRs to nanoparticles of nearly 22%. Suitable characterization techniques such as AFM and SEM have been used to support concept of the proposed growth method.
关键词： direct surface growth,gold nanorods,nanocomposites,atomic force microscopy (AFM),poly(methyl methacrylate) (PMMA)
更新于2025-09-04 15:30:14