Synthesis of Poly(N-H benzamide)-b-poly(lauryl methacrylate)-b-poly(N-H benzamide) symmetrical triblock copolymers by combinations of CGCP, SARA ATRP, and SA ATRC

Synthesis of PDMS-μ-PCL Miktoarm Star Copolymers by Combinations (Є) of Styrenics-Assisted Atom Transfer Radical Coupling and Ring-Opening Polymerization and Study of the Self-Assembled Nanostructures

Due to their diverse and unique physical properties, miktoarm star copolymers (μ-SCPs) have garnered significant attention. In our study, we employed α-monobomoisobutyryl-terminated polydimethylsiloxane (PDMS-Br) to carry out styrenics-assisted atom transfer radical coupling (SA ATRC) in the presence of 4-vinylbenzyl alcohol (VBA) at 0 °C. By achieving high coupling efficiency (χc = 0.95), we obtained mid-chain functionalized PDMS-VBAm-PDMS polymers with benzylic alcohols. Interestingly, matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF MS) analysis revealed the insertion of only two VBA coupling agents (m = 2). Subsequently, the PDMS-VBA2-PDMS products underwent mid-chain extensions using ε-caprolactone (ε-CL) through ring-opening polymerization (ROP) with an efficient organo-catalyst at 40 °C, resulting in the synthesis of novel (PDMS)2-μ-(PCL)2 μ-SCPs. Eventually, novel (PDMS)2-μ-(PCL)2 μ-SCPs were obtained. The obtained PDMS-μ-PCL μ-SCPs were further subjected to examination of their solid-state self-assembly through small-angle X-ray scattering (SAXS) experiments. Notably, various nanostructures, including lamellae and hexagonally packed cylinders, were observed with a periodic size of approximately 15 nm. As a result, we successfully developed a simple and effective reaction combination (Є) strategy (i.e., SA ATRC-Є-ROP) for the synthesis of well-defined PDMS-μ-PCL μ-SCPs. This approach may open up new possibilities for fabricating nanostructures from siloxane-based materials.

Experimental Investigations into the Pyrolysis Mechanism and Composition of Ceramic Precursors Containing Boron and Nitrides with Different Boron Contents

In this work, a novel ceramic precursor containing boron, silicon, and nitrides (named SiBCN) was synthesized from liquid ceramic precursors. Additionally, its pyrolysis, microstructure, and chemical composition were studied at 1600 °C. The results showed that the samples with different boron contents had similar structural composition, and both of the two precursors had stable amorphous SiBN structures at 1400 °C, which were mainly composed of B-N and Si-N and endowed them with excellent thermo-oxidative stability. With the progress of the heating process, the boron contents increased and the structures became more amorphous, significantly improving the thermal stability of the samples in high-temperature environments. However, during the moisture treatment, the introduction of more boron led to worse moisture stability.

SI ATRP for the Surface Modifications of Optically Transparent Paper Films Made by TEMPO-Oxidized Cellulose Nanofibers

Applications of cellulose nanofibers currently match the demands of biodegradable and renewable constituent biocomposites. In this study, we studied the process of preparing TEMPO-oxidized cellulose nanofibers (TOCNs). These nano-sized cellulose fibers (ca. 11 nm) can be fabricated to high transmittance and optically transparent paper (OP) films. Then the OP films can be facilely immobilized initiating sites for the subsequent surface-initiated atom transfer radical polymerization (SI ATRP). We investigated SI ATRP with styrene (St) kinetics and monitored chemical structure changes of the OP surfaces. The obtained OP-g-PSt significantly led to enhance thermal stability and alter the OP surface with hydrophobic compared to that of pristine OP film. Characterization was studied by Fourier transform infrared spectroscopy (FT-IR), powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), UV–Vis spectroscopy, thermogravimetric analyzer (TGA), and water contact angle (WCA) measurements.

Miktoarm Star Copolymers Prepared by Transformation from Enhanced Spin Capturing Polymerization to Nitroxide-Mediated Polymerization (ESCP-Ŧ-NMP) toward Nanomaterials

Reversible-deactivation radical polymerization (RDRP) serves as a powerful tool nowadays for the preparations of unique linear and non-linear macromolecules. In this study, enhanced spin capturing polymerizations (ESCPs) of styrene (St) and tert-butyl acrylate (tBA) monomers were, respectively, conducted in the presence of difunctional (1Z,1'Z)-1,1'-(1,4-phenylene) bis (N-tert-butylmethanimine oxide) (PBBN) nitrone. Four-arm (PSt)4 and (PtBA)4 star macroinitiators (MIs) can be afforded. By correspondingly switching the second monomer (i.e., tBA and St), miktoarm star copolymers (μ-stars) of (PSt)2-μ-(PtBA-b-PSt)2 and (PtBA)2-μ-(PSt-b-PtBA)2) were thus obtained. We further conducted hydrolysis of the PtBA segments to PAA (i.e., poly(acrylic acid)) in μ-stars to afford amphiphilic μ-stars of (PSt)2-μ-(PAA-b-PSt)2 and (PAA)2-μ-(PSt-b-PAA)2. We investigated each polymerization step and characterized the obtained two sets of "sequence-isomeric" μ-stars by FT-IR, 1H NMR, differential scanning calorimeter (DSC), and thermogravimetric analysis (TGA). Interestingly, we identified their physical property differences in the case of amphiphilic μ-stars by water contact angle (WCA) and atomic force microscopy (AFM) measurements. We thus proposed two microstructures caused by the difference of polymer chain sequences. Through this polymerization transformation (Ŧ) approach (i.e., ESCP-Ŧ-NMP), we demonstrated an interesting and facile strategy for the preparations of μ-stars with adjustable/switchable interior and exterior polymer structures toward the preparations of various nanomaterials.

Surface-Initiated Initiators for Continuous Activator Regeneration (SI ICAR) ATRP of MMA from 2,2,6,6-tetramethylpiperidine-1-oxy (TEMPO) Oxidized Cellulose Nanofibers for the Preparations of PMMA Nanocomposites

An effective method of oxidation from paper pulps via 2,2,6,6–tetramethylpiperidine–1–oxy (TEMPO) compound to obtain TEMPO-oxidized cellulose nanofibers (TOCNs) was demonstrated. Following by acylation, TOCN having an atom transfer radical polymerization (ATRP) initiating site of bromoisobutyryl moiety (i.e., TOCN–Br) was successfully obtained. Through a facile and practical technique of surface-initiated initiators for continuous activator regeneration atom transfer radical polymerization (SI ICAR ATRP) of methyl methacrylate (MMA) from TOCN–Br, controllable grafting polymer chain lengths (M_n = ca. 10k–30k g/mol) with low polydispersity (PDI < 1.2) can be achieved to afford TOCN–g–Poly(methyl methacrylate) (PMMA) nanomaterials. These modifications were monitored by Fourier-transform infrared spectroscopy (FT–IR), scanning electron microscopy (SEM), electron spectroscopy for chemical analysis (ESCA), and water contact angle analysis. Eventually, TOCN–g–PMMA/PMMA composites were prepared using the solvent blending method. Compared to the pristine PMMA (T_g = 100 °C; tensile strength (σ_T) = 17.1 MPa), the composites possessed high transparency with enhanced thermal properties and high tensile strength (T_g = 110 °C and σ_T = 37.2 MPa in 1 wt% TOCN containing case) that were investigated by ultraviolet-visible spectroscopy (UV-Vis), thermogravimetric analysis (TGA), dynamic mechanical analysis (DMA), and tensile tests. We demonstrated that minor amounts of TOCN–g–PMMA nanofillers can provide high efficacy in improving the mechanical and thermal properties of PMMA matrix.

Synthesis of Poly(ε-caprolactone)-Based Miktoarm Star Copolymers through ROP, SA ATRC, and ATRP

The synthesis of novel branched/star copolymers which possess unique physical properties is highly desirable. Herein, a novel strategy was demonstrated to synthesize poly(ε-caprolactone) (PCL) based miktoarm star (μ-star) copolymers by combining ring-opening polymerization (ROP), styrenics-assisted atom transfer radical coupling (SA ATRC), and atom transfer radical polymerization (ATRP). From the analyses of gel permeation chromatography (GPC), proton nuclear magnetic resonance (¹H NMR), and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS), well-defined PCL-μ-PSt (PSt: polystyrene), and PCL-μ-PtBA (PtBA: poly(tert-butyl acrylate) μ-star copolymers were successfully obtained. By using atomic force microscopy (AFM), interestingly, our preliminary examinations of the μ-star copolymers showed a spherical structure with diameters of ca. 250 and 45 nm, respectively. We successfully employed combinations of synthetic techniques including ROP, SA ATRC, and ATRP with high effectiveness to synthesize PCL-based μ-star copolymers.

Synthesis of well-defined PCL-b-PnBA-b-PMMA ABC-type triblock copolymers: toward the construction of nanostructures in epoxy thermosets

A novel PCL-b-PnBA-b-PMMA was designed and applied to construct ordered nanostructures within epoxy thermosets.