Polymer Networks for Enrichment of Calcium Ions

In this study, solvogels containing (2-((2-(ethoxycarbonyl)prop-2-en-1-yl)oxy)-ethyl) phosphonic acid (ECPA) and N,N′-diethyl-1,3-bis-(acrylamido)propane (BNEAA) as the crosslinker are synthesized by UV induced crosslinking photopolymerization in various solvents. The polymerization of the ECPA monomer is monitored by the conversion of double bonds with in situ attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy. The morphology of the networks is characterized by in situ photorheology, solid state NMR spectroscopy, and scanning electron microscopy (SEM) of the dried gels. It is demonstrated that the storage modulus is not only determined by the crosslinker content in the gel, but also by the solvent used for preparation. The networks turn out to be porous structures with G′ being governed by a rigid, phase-separated polymer phase rather than by entropic elasticity. The external and internal pKa values of the poly(ECPA-co-BNEAA) gels were determined by titration with a specially designed method and compared to the calculated values. The polymer-immobilized phosphonic acid groups in the hydrogels induce buffering behavior into the system without using a dissolved buffer. The calcium accumulation in the gels is studied by means of a double diffusion cell filled with calcium ion-containing solutions. The successful accumulation of hydroxyapatite within the gels is shown by a combination of SEM, energy-dispersive X-ray spectroscopy (EDX) and wide-angle X-ray scattering (WAXS).

Solid-State Polymerization as a Vitrimerization Tool Starting from Available Thermoplastics: The Effect of Reaction Temperature

In the current work, solid-state polymerization (SSP) was studied for the synthesis of poly(butylene terephthalate), PBT-based vitrimers. A two-step process was followed; the first step involved alcoholysis reactions and the incorporation of glycerol in the polymer chains. The second step comprised transesterification reactions in the solid state (SSP) in the presence of zinc(II) catalyst resulting in the formation of a dynamic crosslinked network with glycerol moieties serving as the crosslinkers. The optimum SSP conditions were found to be 3 h at 180 °C under N2 flow (0.5 L/min) to reach high vitrimer insolubility (up to 75%) and melt strength (2.1 times reduction in the melt flow rate) while increasing the crosslinker concentration (from 3.5 to 7 wt.%) improved further the properties. Glass transition temperature (Tg) was almost tripled in vitrimers compared to initial thermoplastic, reaching a maximum of 97 °C, whereas the melting point (Tm) was slightly decreased, due to loss of symmetry perfection under the influence of the crosslinks. Moreover, the effect of the dynamic crosslinked structure on PBT crystallization behavior was investigated in detail by studying the kinetics of non-isothermal crystallization. The calculated effective activation energy using the Kissinger model and the nucleating activity revealed that the higher crosslinker content impeded and slowed down vitrimers melt crystallization, also inducing an alteration in the crystallization mechanism towards sporadic heterogeneous growth.

Preparation and Characterization of Superabsorbent Polymers Based on Sawdust

Sawdust, a cheap by-product of the timber and forestry industry, was considered as a framework structure to prepare superabsorbent polymer with acrylic acid (AA) and acrylamide (AM), the synthetic monomers. The effects of initiator content, crosslinker content, AA content, AM content, degree of neutralization of AA, and reaction temperature on the swelling rate of superabsorbent polymer were investigated. The synthesized polymer was characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and thermogravimetric analysis (TGA). Under optimal synthesis conditions, the results showed that the swelling rate of the polymer in deionized water and 0.9% NaCl solution reached 738.12 and 90.18 g/g, respectively. The polymer exhibits excellent swelling ability, thermal stability, and reusability. After the polymer was introduced into the samples (soil or coal), the water evaporation rate of the samples was significantly reduced, and the saturated water holding capacity and pore structure were also significantly improved.

Development of Low Dk and Df polyimides for 5G application

We have newly developed non photosensitive and photosensitive polyimide having excellent electrical/mechanical properties. At first we have re-designed the polymer backbone in order to obtain low Dk and Df performance. As a result, our new non photosensitive PI achieved 2.9 of Dk at 20 GHz and 0.003 of Df at 20 GHz. In the next step, we selected the photo package of new PI carefully to maintain both low Dk/Df and high resolution. After that, we modified the photo initiator content, crosslinker content, and so on to have both high lithographic performance and high electrical performance. As a result, new photosentive PI cured at 320 °C showed 3.0 of Dk at 20 GHz and 0.006 of Df at 20 GHz. In addition, this material cured at 200 °C also showed 3.0 of Dk at 20 GHz and 0.009 of Df at 20 GHz. We also confirmed high mechanical properties of new PI. Elongation of this PI cured at >250 °C was approximately 70 %. From lithographic aspects, new PI achieved 15 μm L/S opening with 10 μm thickness.

Morphology and Rheological Properties of Polyacrylamide/Bentonite Organic Crosslinking Composite Gel

The use of polymer gel for water control and oil addition is a common technical method in oilfield development. The polymer and hydrated bentonite react under the action of an organic crosslinking agent to form a composite gel. The particle-size change and microstructure of the composite gel were analyzed via shear thinning, thixotropic, viscoelastic, and start-up stress rheology experiments. The experimental results show that the polyacrylamide/bentonite organic crosslinked composite gel was a gel system with bentonite as the core aggregate structure, and the large particle-size distribution was mostly increased with increasing crosslinker content. The composite gel presented shear thinning characteristics, the content of bentonite or crosslinking agent was increased, and the shear resistance was stronger at a high shear rate. The composite gel exhibited positive thixotropic properties, and the thixotropy increased with increasing bentonite content. The composite gel had good viscoelastic characteristics, the elastic characteristics of the composite gel showed more significantly with bentonite increases, and the viscosity of the composite gel showed its characteristics more significantly with the crosslinking agent increased. After loading at a rate on the composite gel, the shear stress increased significantly with time and reached its maximum value, and then the shear stress decreased and gradually stabilized.

Synthesis of an Aqueous Self-Matting Acrylic Resin with Low Gloss and High Transparency via Controlling Surface Morphology

This paper reports on a novel, film-forming acrylic polymer resin that exhibits low-gloss surface and high transparency via controlling film morphology at sub-micron roughness levels. Such microstructure is controlled by means of the copolymerization process increasing the allyl methacrylate (AMA) crosslinker content from 0 to 0.4 wt %. This acrylic resin makes it possible to avoid high loadings of matting agents, while also having good abrasion resistance and soft-touch feeling. Gloss levels of as low as 4 units at 60° incident angle and light transmittance of up to 85% have been achieved. The chemical structure of the aqueous acrylic resin was characterized by ATR-FTIR and NMR spectroscopy. The film morphology and surface roughness were measured by SEM and AFM analysis. The emulsion particle morphology and glass transition temperature were obtained by TEM and DSC, respectively. The effects of the crosslinker content on the light transmittance, glass transition temperature, and thermal degradation stability were also discussed in detail. The characterization results conclude that an acrylic polymer with interesting optical properties and high thermal stability can be obtained, which is desirable for leather applications.