Study of $$\upbeta $$ β -phase development in spin-coated PVDF thick films

Abstract

A study was conducted to ascertain the effect of variation in spin speed and baking temperature on β-phase content in the spin-coated poly(vinylidene fluoride) (PVDF) thick films (∼4−25 μm). Development of β-phase is dependent on film stretching and crystallization temperature. Therefore, to study the development of β-phase in films, stretching is achieved by spinning and crystallization temperature is adjusted by means of baking. PVDF films are characterized using Fourier transform infrared spectroscopy, X-ray diffraction, differential scanning calorimetry, and scanning electron microscopy. It is observed that crystallization temperature lower than 60 • C and increase in spin speed increases the β-phase content in PVDF films. Crystallization temperature above 60 • C reduces β-phase content and increases α-phase content. It was also observed that viscosity of the PVDF solution affects the β-phase development in films at a particular spin speed.

Phase Inversion in PVDF Films with Enhanced Piezoresponse Through Spin-Coating and Quenching

“…The value of h0 can be estimated experimentally, and it is mainly affected by the wettability of the substrate, by the PVDF-DMF solution viscosity, by the initial angular acceleration of the plate providing a twisting force to the polymer. On the basis of previous studies [10,11] and using Equation (4), we can estimate that for the 20 wt.% PVDF film, h0 is in the range 8–20 μm, whereas for the 30 wt.% PVDF film it is in the range 40–70 μm. The density of the solution, ρ, is calculated using the following expression: ρ=Msolution/Vsolution, where Msolution=mPVDF+mDMF, being mPVDF and mDMF the measured masses of the PVDF and DMF respectively, and Vsolution=mPVDF/ρPVDF+mDMF/ρDMF, considering the density of PVDF …”

“…In References [2,11], the authors investigated the influence on the β-phase formation and the piezoelectric response enhancement of several process parameters. These included the polymer concentration (from 10 to 24 wt.%), the rotational speed ranging from 1000 rpm to 8000 rpm, and the crystallization temperature, in the range from 293 K to 363 K. It was shown that the β-phase increases in general with the rotation speed of the spin-coater, up to a limit value, which increases with the polymer concentration in the solvent.…”

Characterization and Application of PVDF and Its Copolymer Films Prepared by Spin-Coating and Langmuir–Blodgett Method

“…Due to the simple process and good quality of prepared films, there has been a considerable amount of research on prompting the formation of β phase in spin-coated PVDF films [18,22,25,[35][36][37][38][39][40][41][42][43][44][45]. The general process can roughly be divided into three steps: solution preparation, spin-coating, and annealing.…”

“…The nucleation mechanism varies for specific fillers; therefore, important theories such as transcrystallization behavior [47,50] have been set up to describe the main interactions leading to nucleation. In most studies about spin-coating PVDF and its copolymers, the solution concentration is a factor that partially determines the thickness of the resulting film, and the rotational speed is another [25,40,41,43]. Spin-coating generally produces thicker films (>60 nm), but it is reported that films thinner than 10 nm can be achieved with improved experimental conditions [51][52][53].…”

Tourmaline Nanoparticles Doped Polyvinylidene Fluoride (PVDF) Nanofibers

“…Since the piezoelectric property in PVDF is related to the presence and amount of crystal structures in the material, the density changes in the peaks representing the β-crystal structure will inform us about the piezoelectricity of the material. The following formula will be used when making this evaluation [23,30,35]:…”