A novel poly(arylene ether sulfone) (PAES) with pinacol phenylboronate pendants (PAES-B) was prepared by the borylation of brominated PAES (PAES-Br). The reaction was carried out under mild conditions in the presence of cuprous iodide and tri-n-butylphosphine in tetrahydrofuran solution. After heat treatment at 150°C for 132 h, the PAES-B exhibited an interesting solvent resistance. Fourier transform infrared spectroscopy (FTIR) and thermal analysis were performed to investigate the reason. FTIR spectra showed that heat treatment could facilitate losing of pinacol groups and formation of phenylboronic acid in the polymer. Meanwhile, differential scanning calorimetric (DSC) curves demonstrated that the polymer had cross-linking behaviors during heat treatment. In addition, the thermal oxidative stability of PAES-B was researched by the thermogravimetric analysis (TGA).
This article investigates the effect of different microwave powers on the crosslinking behavior and microwave freeze-drying characteristics of wheat starch-lauroyl arginate complex during the microwave freeze-drying process. During microwave freeze-drying, as microwave power increased from 0.1 W/g to 0.9 W/g, the freeze-drying time of WS-LA was reduced by 50 %, while the uniformity of freeze-drying was not affected by its composition. In the research results obtained from DSC, Raman spectroscopy, Fourier-transform infrared spectroscopy (FTIR), XRD, and SEM analyses, with the microwave power increased from 0.1 W/g to 0.9 W/g, the enthalpy value of the melting peak of the WS-LA (wheat starch-lauric acid) composite decreased from 1.15 J/g to 0.62 J/g. The full width at half maximum (FWHM) value increased from 25.6 to 30.79. The ratio of absorbance at 1022/995 cm −1 increased from 1.0111 to 1.0707. The recrystallization (RC) value decreased from 8.77 % to 0.07 %. Additionally, in the microstructure, the size of WS-LA composite particles decreased accordingly. The above findings indicated that the increase in microwave power during microwave freeze-drying had a negative impact on the formation of the WS-LA complex and the ordering of its structure in the sample.
As a semi-crystalline polymer, the influence of crystallization on the crosslinking behavior of polyolefin elastomer (POE) remains unclear, which restricts the enhancement of the crosslinking capability of POE photovoltaic encapsulation films. In this study, we discovered that the crystallization of POE significantly affects its subsequent crosslinking behavior and elucidated the underlying mechanism. Firstly, by comparing the crosslinking behavior and the microstructure of fully crystallized POE and non-crystallized POE, it was found that non-crystallized POE exhibited more thorough crosslinking. This phenomenon indicates that the presence of crystals impedes the complete crosslinking of POE. Subsequently, the mechanism underlying the influence of crystallization on the crosslinking behavior of POE was proposed. The strong exclusion effect of crystallization leads to an uneven distribution of crosslinking agents within the POE matrix, thereby restricting the sufficient crosslinking of POE. In particular, the strong memory effect of POE crystallization results in a localized absence of crosslinking agents in the ethylene-rich regions after melting, further limiting the crosslinking of POE. Finally, we attempted to mitigate the non-uniformity of crosslinking agents’ distribution by regulating the crystal size of POE. Experimental results demonstrated that smaller crystal sizes facilitate more sufficient crosslinking of POE, which further confirms the proposed mechanism. The insights provided in this study could offer inspiration and theoretical guidance for designing the microstructure of POE to enhance the crosslinking ability of POE photovoltaic encapsulation films.
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