Studies of polymerization of acrylic monomers using luminescence probes and differential scanning calorimetry

Abstract

A fiber optic system has been designed to couple calorimeter and fluorimeter equipment for in situ monitoring of polymerization reactions by both techniques simultaneously. Two acrylic monomers (cyclohexyl methacrylate, CHM, and 2-ethylhexyl acrylate, EHA) were studied at different temperatures. Pyrene (Py) was employed at a low concentration (:Sl0-4 mol/L) as a fluorescence probe. The emission spectrum of pyrene shows a broad band peaking at 390 nm, whose intensity grows with polymerization progress. A correlation with conversion degree could be established by collecting fluorescence intensity through the optical fiber at different polymerization times. For the more flexible polymer formed, poly(ethylhexyl acrylate) (PEHA), Py emission sharply increases only when high conversions are reached and continues increasing for a long time after the limiting conversion is attained. For CHM polymerizations, S-shaped curves are found. Isochronal plots of intensity vs. scaled conversion allow elaboration of master curves for the peak emissl. on. Data at 50°C for CHM cannot be fitted to the master curve, and this is explained in terms of vitrification.

Time-intensity superposition for photoinitiated polymerization of fluorinated and hyperbranched acrylate nanocomposites

“…The kinetics of the photoinitiated polymerization of acrylates and methacrylates has been studied by means of photo differential scanning calorimetry (photoDSC) [17][18][19][20][21][22][23], real time Fourier transform infrared analysis (FT-IR) [18,[24][25][26], photorheology [27,28], and fluorescent probe [29,30]. The autocatalytic model has been widely employed to describe the photopolymerization kinetics [17,20,30,31].…”

Development of Cocontinuous Morphologies in Initially Heterogeneous Thermosets Blended with Poly(methyl methacrylate)

“…After mixing, the sample was placed on a preheated sample cell composed of two glass slides and a Teflon spacer (0.5 mm). Epoxy conversion, R, was determined following the extinction of the epoxy band (4532 cm -1 ) referred to a reference C φ-H band (4623 cm -1 ), according to the following expression, where S is the integrated absorbance of the band A built-in optical device 25 was used for measuring the cloud point. It consisted of an optical fiber coupling between a Fluorimeter (Perkin-Elmer LS50B) and a calorimeter (PerkinElmer DSC7).…”

Kinetic study of the cure process at the silica microfibres/epoxy interface using pyrene fluorescence response

“…Fluorescence is a very sensitive and non-destructive technique to monitor curing of different polymeric systems [15][16][17][18][19][20][21][22][23][24]. The use of fluorescen response from labels and probes has become a very powerful tool to follow changes in its surroundings such as polarity and/or rigidity [15][16][17][18][19][20][21][22][23][24][25][26][27].…”

“…The use of fluorescen response from labels and probes has become a very powerful tool to follow changes in its surroundings such as polarity and/or rigidity [15][16][17][18][19][20][21][22][23][24][25][26][27]. Some works propose that an enhancement in the microviscosity of the medium leads to a decrease in the non-radiative decay rate and consequently an increase in the fluorescenc quantum yield [19].…”