About: Polymer is an academic journal. The journal publishes majorly in the area(s): Polymerization & Polymer. It has an ISSN identifier of 0032-3861. Over the lifetime, 32972 publication(s) have been published receiving 1201448 citation(s). The journal is also known as: polymers.
Papers published on a yearly basis
TL;DR: Recent progress in overcoming challenges with regards to effectively delivering hydrogels inside the body without implantation, prolonging the release kinetics of drugs fromhydrogels, and expanding the nature of drugs which can be delivered using hydrogel-based approaches is discussed.
Abstract: There has been considerable progress in recent years in addressing the clinical and pharmacological limitations of hydrogels for drug delivery applications but substantial challenges remain. Here we discuss recent progress in overcoming these challenges, particularly with regards to effectively delivering hydrogels inside the body without implantation, prolonging the release kinetics of drugs from hydrogels, and expanding the nature of drugs which can be delivered using hydrogel-based approaches.
Abstract: In the large field of nanotechnology, polymer matrix based nanocomposites have become a prominent area of current research and development. Exfoliated clay-based nanocomposites have dominated the polymer literature but there are a large number of other significant areas of current and emerging interest. This review will detail the technology involved with exfoliated clay-based nanocomposites and also include other important areas including barrier properties, flammability resistance, biomedical applications, electrical/electronic/optoelectronic applications and fuel cell interests. The important question of the “nano-effect” of nanoparticle or fiber inclusion relative to their larger scale counterparts is addressed relative to crystallization and glass transition behavior. Of course, other polymer (and composite)-based properties derive benefits from nanoscale filler or fiber addition and these are addressed.
Abstract: Graphene-based materials are single- or few-layer platelets that can be produced in bulk quantities by chemical methods. Herein, we present a survey of the literature on polymer nanocomposites with graphene-based fillers including recent work using graphite nanoplatelet fillers. A variety of routes used to produce graphene-based materials are reviewed, along with methods for dispersing these materials in various polymer matrices. We also review the rheological, electrical, mechanical, thermal, and barrier properties of these composites, and how each of these composite properties is dependent upon the intrinsic properties of graphene-based materials and their state of dispersion in the matrix. An overview of potential applications for these composites and current challenges in the field are provided for perspective and to potentially guide future progress on the development of these promising materials.
Abstract: Electrospinning is a process that produces continuous polymer fibers with diameters in the sub-micron range through the action of an external electric field imposed on a polymer solution or melt. Non-woven textiles composed of electrospun fibers have a large specific surface area and small pore size compared to commercial textiles, making them excellent candidates for use in filtration and membrane applications. While the process of electrospinning has been known for over half a century, current understanding of the process and those parameters, which influence the properties of the fibers produced from it, is very limited. In this work, we have evaluated systematically the effects of two of the most important processing parameters: spinning voltage and solution concentration, on the morphology of the fibers formed. We find that spinning voltage is strongly correlated with the formation of bead defects in the fibers, and that current measurements may be used to signal the onset of the processing voltage at which the bead defect density increases substantially. Solution concentration has been found to most strongly affect fiber size, with fiber diameter increasing with increasing solution concentration according to a power law relationship. In addition, electrospinning from solutions of high concentration has been found to produce a bimodal distribution of fiber sizes, reminiscent of distributions observed in the similar droplet generation process of electrospray. In addition, we find evidence that electrostatic effects influence the macroscale morphology of electrospun textiles, and may result in the formation of heterogeneous or three-dimensional structures.
Abstract: In a previous paper it was shown that the complex dielectric constant data of polymers can be represented by an empirical dispersion function. In the present work it is shown that the complex polarization of the same data can be represented by a function of the same form but with different values for the constants. This means that a quantitative evaluation of Scaife's remarks can be made. The dispersion parameters for eighteen polymers were determined for the ϵ∗ (ω) or the ϱ∗ (ω) data. In general, as the ratio ϵ0≥∞ increases, the ϱ∗ (ω) data become broader and faster than the ϵ∗ (ω) data, thus 1 — α, β and τ0 decrease. The normalized loss maximum was found to be temperature dependent [ϵ∗ (ω) data] for eleven polymers where ϵ0≥∞≈2.0. However, the normalized loss maximum [ϵ∗ (ω) data] for the two acetates was found to be independent of temperature while the normalized loss maximum for the ϱ∗ (ω) behaved in a way similar to the other polymers. This observation can be traced to a fortuitous compensation of effects encountered with large dispersions. For those cases where the method of reduced variables is applicable ϵ∗ (ω) calculated from the dispersion function is in good agreement with the shifted values of ϵ∗ (ω). The two parameters α and β are shown to be uniquely related to distribution of relaxation times. The agreement between the distribution function calculated from the dispersion function is in good agreement with the approximate methods used to calculate the function from the shifted data. A complex plane plot of the complex compliance is not at all similar to the dielectric dispersions. An empirical transformation procedure is constructed by analogy with the one used to calculate the complex polarization in order to normalize the mechanical data. The locus of this complex deformation resembles the dielectric dispersion with nearly the same values of α, β and τ0. At very low frequencies, deviations from the assumed behaviour were observed. With polyisobutylene and poly(n-octyl methacrylate) the deviations were in terms of another dispersion. With poly(vinyl acetate) and poly(methyl acrylate) the deviations could be attributed to another low frequency dispersion. The similarity between the dielectric and mechanical dispersions suggests that the following mechanical model can be considered: a spherical inclusion containing the specimen of interest is perfectly bonded to an otherwise continuous homogeneous elastic continuum. Under these conditions the complex distortion of the sphere subjected to a periodic tensile field at infinity is very nearly the empirical complex deformation with Poisson's ratio of 12 for both media. It can also be shown for this model that if the distortion of the sphere is time dependent, then there will be in-phase and out-of-phase components to the distortion in a periodic field. In other words it is not necessary to postulate an internal viscosity to account for a macroscopic viscosity. The equilibrium distortion of the sphere is shown to be related to the square of the asymmetry of the orienting segments. The decay of the distortion with time of the removal of stress field is interpreted in terms of transition probabilities.