Dispersing upconversion nanocrystals in PMMA microfiber: a novel methodology for temperature sensing

The synthesis of a β-NaYF4:Yb3+/Tm3+ phosphor by a thermal decomposition method, focusing on the fabrication of microfibers by the co-doping of nanocrystals with PMMA solution.

Fabrication of asymmetric-gradient-concentric ring patterns via evaporation of droplets of PMMA solution at different substrate temperatures

Asymmetric-gradient-concentric ring patterns are fabricated via evaporating a PMMA solution droplet with a circular copper ring as template. Various micro-patterns are formed in the trench between the polymer rings.

Research on Preparation and Properties of Cellulose Nanofibers and its Polymethylmethacrylate (PMMA) Based Nanocomposites

In this work, the preparation and properties of cellulose nanofibers (CNFs) which have a diameter of less than 100 nm, CNFs sheet and PMMA based nanocomposites sheet were presented. To fabricate CNFs, chemical treatments combined with grinding treatment were used in this research. The CNFs sheet was successfully fabricated by vacuum filtration, and to fabricate the PMMA based nanocomposites sheet, the CNFs sheet was immersed in the PMMA solution, and cured by heat. The tensile strength and Young’s modulus of CNFs sheet is 64.9 MPa and 4438 MPa, respectively. Due to the reinforcement function of CNFs, the tensile strength and Young’s modulus of neat PMMA sheet is improved by 60% and 190%, respectively. The light transmittance of CNFs sheet and PMMA based nanocomposites sheet is 82.1% and 89.2%, respectively.

Electrical Properties of Electrospun Fibers of PANI-PMMA Composites

Electrospinning is one of the simplest techniques for obtaining polymer nano fibers. Nanofibers have large surface area to volume ratio and hence have excellent application potential in sensors, filter design etc. Polyaniline (PANI) is the well-known and widely studied conducting polymer, which however, is insoluble in many common organic solvents and hence difficult to process. PANI in its base form is non conductive but it can be made conducting by protonating with an acids such as hydrochloric acid (HCl) or camphor sulphonic acid (CSA). However, it is difficult to electrospin PANI by itself since we need preferably the polymer in solution form. In this study we have formed nanofibers of PANI (CSA) dispersed in Poly Methyl Methacrylate (PMMA) solution in chloroform. The morphology of the electrospun conducting PMMA-PANI composite fibers is studied using Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM). The DC and AC conductivities of these fibers are measured and the results are discussed.

Electrical Properties of Polymer Composites

Permittivity of about 1 µm thin films prepared from polymethylmetactrylate (PMMA) solution doped with 20 % of diphenyl sulfoxide was studied. Permittivity of the films was measured as a function of the temperature. The measurement of the dependence of polarization on electrical field was performed using a standard Sawyer-Tower circuit. The presence of the dopant increases the composite permittivity namely above the PMMA glass transition temperature. Hysteresis loops observed on the measured polarization vs. electrical field dependence indicate easier and more pronounced polarizability of the composite comparing to pristine PMMA.