Explore the vast range of titles available.

A facile one-step approach to synthesize various phase-separated porous,raspberry-like, flower-like, core-shell and anomalous nanoparticles andnanocapsules via 1,1-diphenylethene （DPE） controlled soap-free emulsioncopolymerization of styrene （S） with glycidyl methacrylate （GMA）, or acrylicacid （AA） is reported. By regulating the mass ratio of S/GMA, transparentpolymer solution, porous and anomalous P（S-GMA） particles could be produced.The P（S-GMA） particles turn from flower-like to raspberry-like and then toanomalous structures with smooth surface as the increase of divinylbenzene（DVB） crosslinker. Transparent polymer solution, nanocapsules and core-shellP（S-AA） particles could be obtained by altering the mole ratio of S/AA; anomalousand raspberry-like P（S-AA） particles are produced by adding DVB. Theunpolymerized S resulted from the low monomer conversion in the presence ofDPE aggregates to form nano-sized droplets, and migrates towards the externalsurfaces of the GMA-enriched P（S-GMA） particles and the internal bulk of theAA-enriched P（S-AA） particles. The nano-sized droplets function as in situporogen, porous P（S-GMA） particles and P（S-AA） nanocapsules are producedwhen the porogen is removed. This novel facile, one-step method with excellentcontrollability and reproducibility will inspire new strategies for creatinghierarchical phase-separated polymeric particles with various structures by simplyaltering the species and ratio of comonomers. The drug loading and releaseexperiments on the porous particles and nanocapsules demonstrate that therelease of doxorubicin hydrochloride is very slow in weakly basic environmentand quick in weakly acidic environment, which enables the porous particlesand nanocapsules with promising potential in drug delivery applications.

Metal‐free polymerization is required to prevent contamination of polymeric materials by residual metal catalysts. In this study, the ring‐opening polymerization (ROP) of ε‐caprolactone (CL) is investigated under bulk conditions at 100°C using benzyl alcohol (BnOH) as the initiator and seven environmentally benign organic acids (EBOAs) as activators (catalysts). In all cases, ROP yields poly(ε‐caprolactone) (PCL) with narrow polydispersities (Ð). Kinetic analysis shows first‐order behavior, indicating a controlled process. The reaction rate constant (k) correlates with the acidity (pKa) of EBOAs, with stronger acids (lower pKa) exhibiting higher catalytic activity among those tested. Substituting BnOH with alternative alcohol initiators produces PCL bearing well‐defined heterotelechelic end groups, such as ally or polyethylene glycol moieties. Hydroxy‐terminated PCL enables further post‐polymerization, including chain extension and block polymerization (poly(ε‐caprolactone)–b–poly(δ‐valerolactone); PCL–b–PVL) with δ‐valerolactone using EBOAs, while preserving narrow Ð. Moreover, the composition unit in PCL–b–PVL can be tuned by selecting EBOAs of different acidity, directly influencing catalytic activity. This controlled EBOA‐based system is useful for applications where metal contamination must be avoided, such as polymeric biomaterials. Ring‐opening polymerization of ε‐caprolactone was performed at 100°C under solvent‐free conditions using catalysts of various environmentally benign organic acids. The reaction rate was correlated with the pKa of the catalysts, and 1H NMR confirmed initiator‐derived chain ends. Block copolymers with δ‐valerolactone was also obtained, exhibiting controlled molecular weights and low polydispersities through the selection of different organic acid catalysts.

Polymers made from natural biomass are gaining interest due to the rising environmental concerns and depletion of petrochemical resources. Lignin isolated from lignocellulosic biomass is the second most abundant natural polymer next to cellulose. The paper pulp process produces industrial lignin as a byproduct that is mostly used for energy and has less significant utility in materials applications. High abundance, rich chemical functionalities, CO2 neutrality, reinforcing properties, antioxidant and UV blocking abilities, as well as environmental friendliness, make lignin an interesting substrate for materials and chemical development. However, poor processability, low reactivity, and intrinsic structural heterogeneity limit lignins′ polymeric applications in high-performance advanced materials. With the advent of controlled polymerization methods such as ATRP, RAFT, and ADMET, there has been a great interest in academia and industry to make value-added polymeric materials from lignin. This review focuses on recent investigations that utilize controlled polymerization methods to generate novel lignin-based polymeric materials. Polymers developed from lignin-based monomers, various polymer grafting technologies, copolymer properties, and their applications are discussed.

Herein, we report a combined computational and experimental investigation into the recently reported universal pyrazole-based reversible addition-fragmentation chain transfer (RAFT) agents (Z−C(=S)−S−R, where Z is 3,5-dimethyl-1H-pyrazol-1-yl), which can mediate controlled radical polymerization of a broad scope of monomers without the need for an additional initiator or catalyst. The results reveal that the high molar absorption coefficient and efficient photolysis kinetics of pyrazole-based chain transfer agents (CTAs) under blue light (λmax = 465 nm) enable rapid radical generation, underpinning ultrafast polymerization of acrylates, acrylamides, methacrylates, and N-vinylpyrrolidone (NVP). While the efficient light absorption is attributed to structural dissimilarity between the Z group and the S–R group (which breaks the local symmetry of the C=S group), the fast photolysis originates from favorable π electron donation from the Z group to the C=S group. Meanwhile, the π electron donation is still weaker than in xanthates, which explains the excellent control of a wide range of monomers, except methacrylates. This work establishes design principles for next-generation CTAs for ultrafast and monomer-universal photoiniferter RAFT polymerization.

Photochemistry has attracted great interest in the last decades in the field of polymer and material science for the synthesis of innovative materials. The merging of photochemistry and reversible-deactivation radical polymerizations (RDRP) provides good reaction control and can simplify elaborate reaction protocols. These advantages open the doors to multidisciplinary fields going from composite materials to bio-applications. Photoinduced Electron/Energy Transfer Reversible Addition-Fragmentation Chain-Transfer (PET-RAFT) polymerization, proposed for the first time in 2014, presents significant advantages compared to other photochemical techniques in terms of applicability, cost, and sustainability. This review has the aim of providing to the readers the basic knowledge of PET-RAFT polymerization and explores the new possibilities that this innovative technique offers in terms of industrial applications, new materials production, and green conditions.

The visualization of organs and tissues using [sup.31]P magnetic resonance (MR) imaging represents an immense challenge. This is largely due to the lack of sensitive biocompatible probes required to deliver a high-intensity MR signal that can be distinguished from the natural biological background. Synthetic water-soluble phosphorus-containing polymers appear to be suitable materials for this purpose due to their adjustable chain architecture, low toxicity, and favorable pharmacokinetics. In this work, we carried out a controlled synthesis, and compared the MR properties, of several probes consisting of highly hydrophilic phosphopolymers differing in composition, structure, and molecular weight. Based on our phantom experiments, all probes with a molecular weight of ~3–400 kg·mol[sup.−1], including linear polymers based on poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC), poly(ethyl ethylenephosphate) (PEEP), and poly[bis(2-(2-(2-methoxyethoxy)ethoxy)ethoxy)]phosphazene (PMEEEP) as well as star-shaped copolymers composed of PMPC arms grafted onto poly(amidoamine) dendrimer (PAMAM-g-PMPC) or cyclotriphosphazene-derived cores (CTP-g-PMPC), were readily detected using a 4.7 T MR scanner. The highest signal-to-noise ratio was achieved by the linear polymers PMPC (210) and PMEEEP (62) followed by the star polymers CTP-g-PMPC (56) and PAMAM-g-PMPC (44). The [sup.31]P T[sub.1] and T[sub.2] relaxation times for these phosphopolymers were also favorable, ranging between 1078 and 2368 and 30 and 171 ms, respectively. We contend that select phosphopolymers are suitable for use as sensitive [sup.31]P MR probes for biomedical applications.

Fluorinated polymers are important materials in everyday life; however, most monomers of widely used fluoropolymers are gaseous, and their polymerization is difficult in an ordinary laboratory. Therefore, partially fluorinated polymers have recently been reported. As an easy-to-handle fluorine-containing monomer, α-trifluoromethylstyrene (TFMST) can be used to produce partially fluorinated polymers with trifluoromethyl groups in the main chain; however, TFMST does not homopolymerize, and there are limited reports on its copolymerization with styrene (ST). In this study, we applied the controlled radical polymerization method, which is effective for the polymerization of ST, to the copolymerization of TFMST and ST. We also showed that nitroxide-mediated polymerization is effective. The content ratio of TFMST in the TFMST–ST copolymer can be controlled between 10% and 40% by changing its monomer ratio. Additionally, the polymerization of TFMST and ST with substituents was performed to increase structural variations. The thermal stability as well as water and oil repellency of the synthesized polymers with different composition ratios and substituents were also evaluated.

The photocatalyst (PC) zinc tetraphenylporphyrin (ZnTPP) is highly efficient for photoinduced electron/energy transfer reversible addition-fragmentation chain transfer (PET-RAFT) polymerization. However, ZnTPP suffers from poor absorbance of orange light by the so-called Q-band of the absorption spectrum (maximum absorption wavelength λmax = 600 nm, at which molar extinction coefficient εmax = 1.0×104 L/(mol·cm)), hindering photo-curing applications that entail long light penetration paths. Over the past decade, there has not been any competing candidate in terms of efficiency, despite a myriad of efforts in PC design. By theoretical evaluation, here we rationally introduce a peripheral benzo moiety on each of the pyrrole rings of ZnTPP, giving zinc tetraphenyl tetrabenzoporphyrin (ZnTPTBP). This modification not only enlarges the conjugation length of the system, but also alters the a1u occupied π molecular orbital energy level and breaks the accidental degeneracy between the a1u and a2u orbitals, which is responsible for the low absorption intensity of the Q-band. As a consequence, not only is there a pronounced hyperchromic and bathochromic effect (λmax = 655 nm and εmax = 5.2×104 L/(mol·cm)) of the Q-band, but the hyperchromic effect is achieved without increasing the intensity of the less useful, low wavelength absorption peaks of the PC. Remarkably, this strong 655 nm absorption takes advantage of deep-red (650–700 nm) light, a major component of solar light exhibiting good atmosphere penetration, exploited by the natural PC chlorophyll a as well. Compared with ZnTPP, ZnTPTBP displayed a 49% increase in PET-RAFT polymerization rate with good control, marking a significant leap in the area of photo-controlled polymerization.

The recent development in polymer science has gone beyond the traditional linear and randomly functionalizable macromolecules to the architected polymer systems, which integrate modular synthesis and dynamic responsiveness. Although the literature related to polymer synthesis and stimuli-responsive materials and applications is widely discussed, it is common to review the aspects independently, restricting a complete picture of how architectural modularity controls adaptive performance. This gap is filled in this review with an integrated framework of relating modular polymer synthesis, stimuli-responsive design, and application-oriented functionality in a single coherent design philosophy. The scientific novelty of this review is that the focus on modular polymers is not only on synthetic constructs, but is a programmable functional scaffold where the structural precision is the direct determinant of responsiveness, multifunctionality, and performance. Controlled polymerization and post-polymerization modification regimes are mentioned to be tools that allow precise positioning of functional modules, and this allows polymers to respond in predictable ways to environmental stimuli like pH, temperature, light, redox conditions, etc. In addition, the review identifies the role of a synergistic combination of various responsive modules in the emergence of behaviours that would not be reached in conventional polymer systems. This review offers a coherent viewpoint on the future of functional polymers of the next generation by bringing together synthetic approaches to nano-responsive behaviour and real-world technologies, such as drug delivery, self-healing surfaces, adaptive surfaces, and biosensing surfaces. The framework in the present paper provides a logical route towards the development of environmentally friendly, multifunctional, and adjustable polymer structures.

Well-defined poly( N -allyl alanine) has been synthesized by heterogenous ring-opening polymerization (HROP) of less reactive N -allyl-alanine N -carboxyanhydride, using acetic acid as the catalyst and benzylamine as the initiator, in non-polar n -hexane. Interestingly, the polymerization exhibited typical features of living polymerization though both monomer (liquid) and polymer (solid) have minimal solubility in n -hexane. The obtained polymer showed a stable helix structure independent of the temperatures screened, as evidenced by circular dichroism analysis. Also, the preliminary study demonstrated that the side chains can be post-functionalized through thiol-ene click chemistry with quantitative conversion. Together, this work provides guidance for the development of accelerated HROP of other liquid monomers bearing low reactivity. Besides, the helical and functionalizable poly( N -allyl alanine) could be a useful “clickable platform” for the design of variable biomaterials via efficient click chemistry.