Showing papers in "Advances in Polymer Science in 2015"
TL;DR: Self-nucleation (SN) as discussed by the authors is a special nucleation process triggered by self-seeds or selfnuclei that are generated in a given polymeric material by specific thermal protocols or by inducing chain orientation in the molten or partially molten state.
Abstract: Self-nucleation (SN) is a special nucleation process triggered by self-seeds or self-nuclei that are generated in a given polymeric material by specific thermal protocols or by inducing chain orientation in the molten or partially molten state. SN increases the nucleation density of polymers by several orders of magnitude, producing significant modifications to their morphology and overall crystallization kinetics. In fact, SN can be used as a tool for investigating the overall isothermal crystallization kinetics of slow-crystallizing materials by accelerating the primary nucleation stage in a previous SN step. Additionally, SN can facilitate the formation of one particular crystalline phase in polymorphic materials. The SN behavior of a given polymer is influenced by its molecular weight, molecular topology, and chemical structure, among other intrinsic and extrinsic characteristics. This review paper focuses on the applications of DSC-based SN techniques to study the nucleation, crystallization, and morphology of different types of polymers, blends, copolymers, and nanocomposites.
107 citations
TL;DR: In this article, a non-imidazolium-based ionic liquid, 1,5-diazabicyclo[430]non-5-enium acetate, was used as an excellent solvent for cellulose fiber spinning.
Abstract: The constant worldwide increase in consumption of goods will also affect the textile market The demand for cellulosic textile fibers is predicted to increase at such a rate that by 2030 there will be a considerable shortage, estimated at ~15 million tons annually Currently, man-made cellulosic fibers are produced commercially via the viscose and Lyocell™ processes Ionic liquids (ILs) have been proposed as alternative solvents to circumvent certain problems associated with these existing processes We first provide a comprehensive review of the progress in fiber spinning based on ILs over the last decade A summary of the reports on the preparation of pure cellulosic and composite fibers is complemented by an overview of the rheological characteristics and thermal degradation of cellulose–IL solutions In the second part, we present a non-imidazolium-based ionic liquid, 1,5-diazabicyclo[430]non-5-enium acetate, as an excellent solvent for cellulose fiber spinning The use of moderate process temperatures in this process avoids the otherwise extensive cellulose degradation The structural and morphological properties of the spun fibers are described, as determined by WAXS, birefringence, and SEM measurements Mechanical properties are also reported Further, the suitability of the spun fibers to produce yarns for various textile applications is discussed
81 citations
TL;DR: An overview of some paradigmatic and well-studied examples of self-repair in living systems is provided, including a number of case studies that provide a detailed description of the structure–function relationships defining the healing mechanism.
Abstract: Damage and fatigue are ever-present facts of life. Given enough time, even the most robust material, whether man-made or natural, succumbs to the deleterious effects of cracks, fissures, and defects during normal use. Traditionally, materials engineers have approached this problem by creating damage-tolerant structures, intensive quality control before use, vigilant inspection during use, and designing materials to function well below their theoretical limit. Living organisms, on the other hand, routinely produce materials that function close to their theoretical limit as a result of their remarkable ability to self-heal a range of non-catastrophic damage events. For this reason, many researchers in the last 15 years have turned to nature for inspiration for the design and development of self-healing composites and polymeric materials. However, these efforts have so far only scratched the surface of the richness of natural self-repair processes. In the present review, we provide an overview of some paradigmatic and well-studied examples of self-repair in living systems. The core of this overview takes the form of a number of case studies that provide a detailed description of the structure–function relationships defining the healing mechanism. Case studies include a number of examples dependent on cellular action in both animals (e.g., limb regeneration, antler growth, bone healing, and wound healing) and plants (e.g., latex-based healing, plant grafting, and wound closure in woody vines and succulent plants). Additionally, we examine several examples of acellular self-repair in biopolymeric materials (e.g., mussel byssus, caddisfly silks, and whelk egg capsules) that are already inspiring the development of a number of self-healing polymers.
51 citations
TL;DR: A review of state-of-the-art techniques for the characterization of polymer healing occurring at the microscopic and macroscopic levels during the repair of damage such as scratches, cracks, or ballistic perforations can be found in this paper.
Abstract: Over the last few years, several testing methods have been introduced for the detection and quantification of autonomous and thermally stimulated healing in polymers. This review summarizes some of the most prominent state-of-the-art techniques for the characterization of polymer healing occurring at the microscopic and macroscopic levels during the repair of damage such as scratches, cracks, or ballistic perforations. In addition to phenomenological investigation of the self-healing process, a range of physical characterization techniques have been explored for elucidation of the underlying healing mechanism at the molecular or polymer network level. The present state of visual methods, spectroscopic techniques, scattering techniques, and dynamic methods is described. A short outlook is provided, discussing the future challenges and expected new trends in the characterization of self-healing polymers.
47 citations
TL;DR: In this article, the cellulose crystallinity index (CI) of a set of reference samples were determined from X-ray diffraction (XRD), nuclear magnetic resonance (NMR), and infrared (IR), Raman, and vibrational sum frequency generation (SFG) spectroscopy.
Abstract: Although the cellulose crystallinity index (CI) is used widely, its limitations have not been adequately described. In this study, the CI values of a set of reference samples were determined from X-ray diffraction (XRD), nuclear magnetic resonance (NMR), and infrared (IR), Raman, and vibrational sum frequency generation (SFG) spectroscopies. The intensities of certain crystalline peaks in IR, Raman, and SFG spectra positively correlated with the amount of crystalline cellulose in the sample, but the correlation with XRD was nonlinear as a result of fundamental differences in detection sensitivity to crystalline cellulose and improper baseline corrections for amorphous contributions. It is demonstrated that the intensity and shape of the XRD signal is affected by both the amount of crystalline cellulose and crystal size, which makes XRD analysis complicated. It is clear that the methods investigated show the same qualitative trends for samples, but the absolute CI values differ depending on the determination method. This clearly indicates that the CI, as estimated by different methods, is not an absolute value and that for a given set of samples the CI values can be compared only as a qualitative measure.
35 citations
TL;DR: This review focuses on the research activities in the area of (co-)poly(2-oxazoline)s prepared by microwave-assisted syntheses and summarizes the current-state-of-the-art of the microwave- assisted synthesis of 2-oxzoline monomers and the microwaves-assisted ring-opening ( co-)polymerization of 2 -oxazolines.
Abstract: More than any other polymer class, the synthesis of (co-)poly(2-oxazoline)s has benefited tremendously from the introduction of microwave reactors into chemical laboratories. This review focuses on research activities in the area of (co-)poly(2-oxazoline)s prepared by microwave-assisted syntheses and summarizes the current state-of-the-art for microwave-assisted syntheses of 2-oxazoline monomers, microwave-assisted ring-opening (co-)polymerizations of 2-oxazolines, and prominent examples of post-polymerization modifications of (co-)poly(2-oxazoline)s. Special attention is paid to kinetic analyses of the microwave-assisted polymerization of 2-oxazolines and to the discussion of non-thermal microwave effects.
23 citations
TL;DR: In this article, concomitant crystallization and cross-nucleation between poly(pivalolactone) polymorphs are discussed. And the authors present two relevant examples taken from their own work.
Abstract: Crystallization of polymorphic polymers can lead to different structures, starting from the same melt or solution. Comprehensive understanding of crystallization modalities in such systems is of primary technological and scientific relevance, because it can enable prediction – and possible control – of the polymorphic composition of a material and, in turn, of its properties. Several structuring pathways are possible. A given structure can develop either directly or through successive metastable states. The latter case obeys the so-called Ostwald’s rule of stages. Under particular thermodynamic and kinetic conditions, two or more polymorphs can nucleate and grow concomitantly. Moreover, cross-nucleation is observed when a faster growing polymorph nucleates on a previously existing polymorph. This chapter is focused on concomitant crystallization and cross-nucleation between polymer polymorphs, two topics that have seldom been considered in the past and lack critical review. First, the scattered pieces of information in the polymer literature are collected and discussed. Within this framework, we present two relevant examples taken from our own work, concerning concomitant crystallization of poly(pivalolactone) polymorphs and cross-nucleation in seeded crystallization of isotactic poly(1-butene).
19 citations
TL;DR: In this article, reversible addition-fragmentation chain transfer (RAFT) polymerization-based surface modification has emerged as a powerful tool for preparation of well-defined polymers grafted solid substrates.
Abstract: Reversible addition–fragmentation chain transfer (RAFT) polymerization-based surface modification has emerged as a powerful tool for preparation of well-defined polymers grafted solid substrates. Combination of the RAFT process with highly efficient ligation reactions involving click chemistry can further extend its application in controlled synthesis of functional hybrid and composite materials. This review highlights some basic features of this method and describes synthesis of polymer-grafted solid surfaces such as silica particles, metal oxide, gold nanoparticles, cellulose, and graphene oxide. Applications of such functional materials, including their use in functional additives, bioactive surfaces and biomaterials, stationary phases for chromatographic applications, and preparation of hollow capsules and molecularly imprinted polymer films, are also summarized.
18 citations
TL;DR: In this article, the main quantities that can be extracted from SAXS and WAXD experiments on semicrystalline polymers and shows the most recent results on real-time investigation of polymer structuring with millisecond time resolution.
Abstract: In industrial processes, polymer melts are often exposed to a combination of fast cooling rates, high flow fields, and high pressures. The processing conditions have an ultimate impact on the structure that develops during cooling. The final structure at the nano- and microscopic level determines the properties of the final polymer product. Small and wide angle X-ray scattering and diffraction (SAXS/WAXD) are the best techniques for investigating in-situ and real-time fast polymer structuring at a scale ranging from 0.1 to 100 nm. This contribution reviews the main quantities that can be extracted from SAXS and WAXD experiments on semicrystalline polymers and shows the most recent results on real-time investigation of polymer structuring with millisecond time resolution. Examples of structuring during fast cooling, flow in confined geometry, and uniaxial stretching are discussed. Future directions for the use of synchrotron SAXS/WAXD to study fast polymer structuring are also discussed.
14 citations
TL;DR: A review of cellulose accessibility, structure, and function with a particular focus on its interactions with deuteration is presented in this article, highlighting remarkable new findings in cellulose research as a result of the development of new experimental approaches.
Abstract: This contribution summarizes achievements in the understanding of cellulose accessibility, structure, and function with a particular focus on its interactions with deuteration. This review is the first to explicitly devote a discussion to deuteration of cellulose and highlights remarkable new findings in cellulose research as a result of the development of new experimental approaches, from simple weighing of deuterated samples to sophisticated techniques such as small angle neutron scattering and 2H-NMR spectroscopy.
11 citations
TL;DR: Aromatic hyperbranched polymers: Synthesis and Application. as discussed by the authors, changing polymer solvation by Electrochemical Means: Basics and Applications. And, the use of porous carbons from plastic waste.
Abstract: Porous Carbons from Plastic Waste.- Aromatic Hyperbranched Polymers: Synthesis and Application.- Changing Polymer Solvation by Electrochemical Means: Basics and Applications.
TL;DR: This chapter gives an overview of translational research on different supramolecular hydrogels, showing systems that have been used in vivo in the field of regenerative medicine, and discusses tuning of the mechanical properties and functionalization of thesehydrogels with bioactive compounds.
Abstract: Regenerative medicine is the science of re-creating or repairing living functional tissue, often inside the body. Biomaterials for regenerative medicine are inspired by the extracellular matrix (ECM), which provides the natural scaffold for cells inside the body. The use of supramolecular hydrogels as man-made tunable replacements for the ECM is being investigated because hydrogels offer an aqueous environment. In addition, supramolecular systems offer modularity and dynamics, also found in the ECM. This chapter gives an overview of translational research on different supramolecular hydrogels, showing systems that have been used in vivo in the field of regenerative medicine. We discuss the chemical structures and biomedical applications of various natural compounds, biosynthetic compounds, biohybrid systems, and fully synthetic materials. Furthermore, we discuss tuning of the mechanical properties and functionalization of these hydrogels with bioactive compounds. Both characteristics are essential for their function in contact with cells and for the creation of a regenerative niche, thereby controlling cellular adherence, proliferation, homing, and differentiation.