Synthesis of poly(2-ethylhexyl acrylate)/clay nanocomposite by in situ living radical polymerization

Electrical and Photodetector Characteristics of Schottky Structures Interlaid with P(EHA) and P(EHA-co-AA) Functional Polymers by the iCVD Method

In this study, poly(2-ethylhexyl acrylate) (PEHA) homopolymer and its copolymer combined with acrylic acid P(EHA-co-AA) were employed as interfaces in two separate Schottky structures. First, both interfaces were grown by initiated chemical vapor deposition (iCVD), which provides much better deposition control and homogeneous coating compared to solution-phase methods. In addition to this advantageous method, the effects of two different polymers, one of which is better able to adhere to the crystal surface on which it is formed than the other, on the optoelectronic properties have been studied. Then, their current-voltage (I-V) and capacitance/conductance-voltage (C/(G/ω)-V) characteristics were investigated both in the dark and under illumination. The basic electrical parameters and the illumination-induced profile of the surface state (Nss) were probed by I-V and C-V measurements for two samples. A decrease in the barrier height (BH) and, consequently, a significant increase in the photocurrent were observed under illumination. Striking changes in series resistance (Rs) values are also highlighted. The photocapacitance and conductance characteristics indicated that the structures could be considered not only as photodiodes but also as photocapacitors. Moreover, the voltage-dependent changes of some photodetector parameters, such as responsivity (R), sensitivity (S), and specific detectivity (D*), along with the transient photocurrent characteristics, are discussed for both structures. Therefore, we can say that the strong changes in these parameters, which figure the merit of photodiode and photodetector applications, depending on the voltage and under illumination, prove that it is a study carried out in accordance with the purpose and so they can be used in electronic and optoelectronic applications.

Thermal Degradation Studies of Poly(2-ethyl hexyl acrylate) in the Presence of Nematic Liquid Crystals

The thermal degradation behavior of Poly(2-ethyl hexyl hcrylate) (Poly(2-EHA)), blended with a commercially available nematic liquid crystal (LC) mixture, was investigated by thermal gravimetric analysis (TGA). Different heating rates, ranging from 5 to 200 °C/min, were applied under an inert atmosphere. Based on the TGA results, activation energies (Eα) at different conversion rates (α) were determined using three integral isoconversion methods: Flynn-Wall-Ozawa (FWO), Tang, and Kissinger-Akahira-Sunose (KAS). It can be noticed that the global evolution of these activation energies was the same for the three models. The coefficient of determination R2 presented values generally higher than 0.97. Using these models, the Eα value for the LC remains constant at 64 kJ/mol for all conversions rates. For the polymer Poly(2-EHA), applying the Tang and FWO models, the activation energy presents a variation ranging from 80 kJ/mol, for conversion α = 0.1, to 170 kJ/mol, for α = 0.9. For the third model (KAS), this energy varies between 80 and 220 kJ/mol in the same range of α.

Recent advances in RDRP-modified chitosan: a review of its synthesis, properties and applications

RDRP modified Chitosan exhibits improved hydrophobic, cationic and anionic properties, which make them more useful in diversified applications. This review delineates the recent advancement in RDRP-modified chitosan and their properties.

Modeling of the Free Radical Copolymerization Kinetics of n-Butyl Acrylate, Methyl Methacrylate and 2-Ethylhexyl Acrylate Using PREDICI®

Kinetic modeling of the bulk free radical copolymerizations of n-butyl acrylate (BA) and 2-ethylhexyl acrylate (EHA); methyl methacrylate (MMA) and EHA; as well as BA, MMA and EHA was performed using the software PREDICI®. Predicted results of conversion versus time, composition versus conversion, and molecular weight development are compared against experimental data at different feed compositions. Diffusion-controlled effects and backbiting for BA were incorporated into the model as they proved to be significant in these polymerizations. The set of estimated global parameters allows one to assess the performance of these copolymerization systems over a wide range of monomer compositions.

Investigating the Effect of Silica Aerogel Nanoparticles on the Kinetics of AGET ATRP of Methyl Methacrylate

Hexamethyldisilazane-modified silica aerogel nanoparticles were used for in situ polymerization of methyl methacrylate by activators generated by electron transfer for atom transfer radical polymerization (AGET ATRP) to synthesize tailor-made PMMA nanocomposites. Appropriate dispersion of silica aerogel nanoparticles in the monomer solution and improvement in interfacial interaction between the PMMA matrix and nanoparticles are two main reasons for application of HMDS-modified silica aerogel nanoparticles. Nitrogen adsorption/desorption isotherm was employed to examine surface area and structural characteristics of the HMDS-modified silica aerogel nanoparticles. Evaluation of size distribution and morphological studies were also performed by SEM and TEM. Conversion and molecular weight determinations were carried out using GC and SEC, respectively. Addition of 3 wt% HMDS-modified silica aerogel nanoparticles leads to decrement of conversion from 85 to 64%. Molecular weight of PMMA chains also decreases from 13,912 to 10,810 g⋅mol−1 by addition of only 3 wt% HMDS-modified silica aerogel nanoparticles; however, polydispersity index values increases from 1.18 to 1.51. Linear increase of ln(M0/M) with time for all the samples shows that polymerization proceeds in a living manner. In addition, suitable agreement between theoretical and experimental molecular weight in combination with low PDI values can appropriately demonstrate the living nature of the polymerization. TGA results indicate that by increasing HMDS-modified silica aerogel nanoparticles content, slight improvements in thermal stability of the nanocomposites were obtained. DSC results show a decrease in Tg from 86.9 to 80.1°C by addition of 3 wt% HMDS-modified silica aerogel nanoparticles.

Acetone: a solvent or a reagent depending on the addition order in SET-LRP

The importance of reagent order in biphasic SET-LRP in acetone/water mixtures is shown.

Recent Developments in the Synthesis of Biomacromolecules and their Conjugates by Single Electron Transfer-Living Radical Polymerization

Single electron transfer-living radical polymerization (SET-LRP) represents a robust and versatile tool for the synthesis of vinyl polymers with well-defined topology and chain end functionality. The crucial step in SET-LRP is the disproportionation of the Cu(I)X generated by activation with Cu(0) wire, powder, or nascent Cu(0) generated in situ into nascent, extremely reactive Cu(0) atoms and nanoparticles and Cu(II)X₂. Nascent Cu(0) activates the initiator and dormant chains via a homogeneous or heterogeneous outer-sphere single-electron transfer mechanism (SET-LRP). SET-LRP provides an ultrafast polymerization of a plethora of monomers (e.g., (meth)-acrylates, (meth)-acrylamides, styrene, and vinyl chloride) including hydrophobic and water insoluble to hydrophilic and water soluble. Some advantageous features of SET-LRP are (i) the use of Cu(0) wire or powder as readily available catalysts under mild reaction conditions, (ii) their excellent control over molecular weight evolution and distribution as well as polymer chain ends, (iii) their high functional group tolerance allowing the polymerization of commercial-grade monomers, and (iv) the limited purification required for the resulting polymers. In this Perspective, we highlight the recent advancements of SET-LRP in the synthesis of biomacromolecules and of their conjugates.

Acetone–water biphasic mixtures as solvents for ultrafast SET-LRP of hydrophobic acrylates

Transformation of SET-LRP catalyzed with Cu(0) wire from single phase (acetone/water = 9/1, v/v) into biphase (acetone/water = 8/2, v/v).

SET-LRP mediated by TREN in biphasic water–organic solvent mixtures provides the most economical and efficient process

Screening ligands and solvents for economical and efficient biphasic SET-LRP.

Cu(0)-mediated living radical polymerization: recent highlights and applications; a perspective

Cu(0)-mediated living radical polymerization or single electron transfer living radical polymerization (Cu(0)-mediated LRP or SET-LRP) is a versatile polymerization technique that has attracted considerable interest during the past few years for the facile preparation of advanced materials.

Photo-induced SI-ATRP for the synthesis of photoclickable intercalated clay nanofillers

Design of functional and hairy nanoclay intercalated assemblies using tandem photoinduced surface initiated ATRP-1,3 dipolar cycloaddition/thiol-yne click reactions.

Acrylic AB and ABA block copolymers based on poly(2-ethylhexyl acrylate) (PEHA) and poly(methyl methacrylate) (PMMA) via ATRP

Acrylic block copolymers have several advantages over conventional styrenic block copolymers, because of the presence of a saturated backbone and polar pendant groups. This investigation reports the preparation and characterization of di- and triblock copolymers (AB and ABA types) of 2-ethylhexyl acrylate (EHA) and methyl methacrylate (MMA) via atom transfer radical polymerization (ATRP). A series of block copolymers, PEHA-block-PMMA(AB diblock) and PMMA-block-PEHA-block-PMMA(ABA triblock) were prepared via ATRP at 90 °C using CuBr as catalyst in combination with N,N,N',N″,N″-pentamethyl diethylenetriamine (PMDETA) as ligand and acetone as additive. The chemical structure of the macroinitiators and molar composition of block copolymers were characterized by (1)H NMR analysis, and molecular weights of the polymers were analyzed by GPC analysis. DSC analysis showed two glass transition temperatures (T(g)), indicating formation of two domains, which was corroborated by AFM analysis. Small-angle X-ray scattering (SAXS) analysis of AB and ABA block copolymers showed scattering behavior inside the measuring limits indicating nanophase separation. However, SAXS pattern of AB diblock copolymers indicated general phase separation only, whereas for ABA triblock copolymer an ordered or mixed morphology could be deduced, which is assumed to be the reason for the better mechanical properties achieved with ABA block copolymers than with the AB analogues.