Boron-Catalyzed Polymerization of Phenyl-Substituted Allylic Arsonium Ylides toward Nonconjugated Emissive Materials from C3/C1 Monomeric Units

Two novel allylic arsonium ylide monomers with a phenyl (steric and electronic effect) group at different positions were synthesized and used in boron-catalyzed polymerization to produce a series of well-defined polymers, poly­(2-phenyl-propenylene-co-2-phenyl-propenylidene) (P2-PhAY) and poly­(3-phenyl-propenylene-co-3-phenyl-propenylidene) (P3-PhAY), with unusual structures but a controllable molecular weight and relatively low polydispersity. The backbone of these polymers consists of a mixture of C1 (chain grows by one carbon atom at a time) and C3 (chain grows by three carbon atoms at a time) monomeric units, as determined by 1H, 13C, and 1H–13C HSQC 2D NMR. Based on the experimental results and density functional theoretical (DFT) calculations, we were able to propose a mechanism that takes into account not only the steric hindrance, but also the electron effect of the phenyl group. In addition, a nontraditional intrinsic luminescence was observed from the nonconjugated P2-PhAY and P3-PhAY; such unexpected emission is attributed to the formation of C3-unit clusters, as evidenced by ultraviolet–visible and fluorescence spectroscopy

Well-Defined Bilayered Molecular Cobrushes with Internal Polyethylene Blocks and ω‑Hydroxyl-Functionalized Polyethylene Homobrushes

Novel well-defined bilayered molecular cobrushes with internal polyethylene blocks, P­(PE_core-<i>b</i>-PS_corona) (PE: polyethylene; PS: polystyrene), and ω-hydroxyl-functionalized polyethylene homobrushes, P­(PE-OH), were synthesized through the macromonomer strategy. Two main steps were involved in the synthesis of the P­(PE_core-<i>b</i>-PS_corona) bilayered cobrushes: (i) formation of norbornyl-terminated macromonomer (Nor-PE-<i>b</i>-PS) by esterification of PS-<i>b</i>-PE-OH (combination of anionic polymerization, hydroboration, and polyhomologation) with 5-norbornene-2-carboxylic acid and (ii) ring-opening metathesis polymerization (ROMP) of Nor-PE-<i>b</i>-PS. The synthesis of P­(PE-OH) was achieved by (i) hydroboration of <i>tert</i>-butyl­dimethyl­silyl-protected allyl alcohol, followed by polyhomologation of dimethyl­sulfoxoniun methylide with the formed tri­[3-(<i>tert</i>-butyl­dimethyl­silyl­oxyl)­propyl]­borane initiator, oxidation/hydrolysis, and esterification of the TBDMS-O-PE-OH with 5-norbornene-2-carboxylic acid to afford the macromonomer TBDMS-O-PE-Nor, and (ii) ROMP of TBDMS-O-PE-Nor, followed by deprotection. Nuclear magnetic resonance spectroscopy (¹H and ¹³C NMR) and high temperature gel permeation chromatography (HT-GPC) were used to characterize all macromonomers/molecular brushes and differential scanning calorimetry (DSC) to study the thermal properties. The molecular brush P­(PE-<i>b</i>-PS) showed lower melting point (<i>T</i>_m) and better solubility in toluene than the corresponding macromonomer PS-<i>b</i>-PE-Nor. In the case of homobrushes, the thermal properties were strongly affected by the presence of the PE end-groups

Tetraphenylethene-Functionalized Polyethylene-Based Polymers with Aggregation-Induced Emission

A novel synthetic strategy toward a series of tetraphenylethene (TPE)-functionalized polyethylene-based homo/copolymers is presented. Tris­(3-(4-(1,2,2-triphenyl­vinyl)­phenoxy)­propyl)­borane, synthesized by hydroboration of (2-(4-(allyloxy)­phenyl)­ethene-1,1,2-triyl)­tribenzene with BH3, was used to initiate the polyhomologation of dimethyl­sulfoxonium methylide to afford well-defined TPE-terminated linear polyethylene (PE). Combining this efficient strategy with ring-opening polymerization (ROP) or atom transfer radical polymerization (ATRP), TPE-functionalized PE-based block copolymers have been synthesized. All synthesized polymers showed aggregation-induced emission (AIE) behavior either in solution or in bulk. Self-assembly of the PE-based block copolymer in DMF resulted in strong emission due to the AIE effect of the aggregated TPE-PM core; the fluorescence intensity of the solution is directly related to the composition of block copolymers and the size of the micelle. The response of the AIE-operative fluorescence behavior in terms of concentration of the block copolymer solutions has also been used to locate the critical micelle concentration (CMC) value of the block copolymers. The nonemissive dilute solutions of block copolymers became fluorescent when increasing concentrations above the CMC

Temperature and pH-Dual Responsive AIE-Active Core Crosslinked Polyethylene–Poly(methacrylic acid) Multimiktoarm Star Copolymers

A series of aggregation-induced emission (AIE) active core crosslinked miktoarm star copolymers, having multi polyethylene (PE) and poly­(methacrylic acid) (PMAA) arms, were synthesized and their thermal/pH responsive properties were studied. The procedure involves (a) the synthesis of PE-Br by polyhomologation of dimethylsulfoxonium methylide with triethylborane as initiator, followed by oxidation-hydrolysis/esterification reactions and of poly­(<i>tert</i>-butyl methacrylate) (P<i>t</i>BMA-Br) by atom transfer radical polymerization (ATRP) of <i>tert</i>-butyl methacrylate, (b) the synthesis of (PE)_<i>n</i>-(P<i>t</i>BMA)_<i>m</i>-P­(TPE-2St) by ATRP of a double styrene-functionalized tetraphenylethene (TPE-2St) with PE-Br and P<i>t</i>BMA-Br macroinitiators, and (c) the hydrolysis of (PE)_<i>n</i>-(P<i>t</i>BMA)_<i>m</i>-P­(TPE-2St) to afford the amphiphilic miktoarm star copolymers (PE)_<i>n</i>-(PMMA)_<i>m</i>-P­(TPE-2St). Due to their spherical core–shell structure (temperature-responsive) and the presence of hydrophilic PMAA (pH-responsive) and TPE-2St (AIE), these miktoarm star copolymers are AIE materials with temperature/pH-dual responsivity. In addition, thanks to the coexistence of hydrophilic and hydrophobic arms, these materials promote stable water-in-oil emulsions

Living/Controlled Anionic Polymerization of Glycolide in Fluoroalcohols: Toward Sustainable Bioplastics

Ring-opening polymerization (ROP) is a promising approach to accessing well-defined polyesters with superior (bio)degradability and recyclability. However, the living/controlled polymerization of glycolide (GL), a well-known sustainable monomer derived from carbon monoxide/dioxide, has never been reported due to the extremely low solubility of its polymer in common solvents. Herein, we report the first living/controlled anionic ROP of GL in strong protic fluoroalcohols (FAs), which are conventionally considered incompatible with anionic polymerization. Well-defined polyglycolide (PGA, Đ Mn up to 55.4 kg mol–1) and various PGA-based macromolecules are obtained at room temperature for the first time. NMR titration and computational studies revealed that FAs simultaneously activate the chain end and monomer without being involved in initiation. Low-boiling-point FAs and PGA can be recycled through simple distillation and sublimation at 220 °C in vacuo, respectively, providing a promising sustainable alternative for tackling plastic pollution problems

Fast and Living Ring-Opening Polymerization of α‑Amino Acid <i>N</i>‑Carboxyanhydrides Triggered by an “Alliance” of Primary and Secondary Amines at Room Temperature

A novel highly efficient strategy, based on an “alliance” of primary and secondary amine initiators, was successfully developed allowing the fast and living ring-opening polymerization (ROP) of α-amino acid <i>N</i>-carboxyanhydrides (NCAs) at room temperature

Poly(dl-lactide)-<i>b</i>-poly(<i>N,N</i>-dimethylamino-2-ethyl methacrylate): Synthesis, Characterization, Micellization Behavior in Aqueous Solutions, and Encapsulation of the Hydrophobic Drug Dipyridamole

We synthesized a series of well-defined poly(dl-lactide)-b-poly(N,N-dimethylamino-2-ethyl methacrylate) (PDLLA-b-PDMAEMA) amphiphilic diblock copolymers by employing a three-step procedure: (a) ring-opening polymerization (ROP) of dl-lactide using n-decanol and stannous octoate, Sn(Oct)2, as the initiating system, (b) reaction of the PDLLA hydroxyl end groups with bromoisobutyryl bromide, and (c) atom transfer radical polymerization, ATRP, of DMAEMA with the newly created bromoisobutyryl initiating site. The aggregation behavior of the prepared block copolymers was investigated by dynamic light scattering and ζ potential measurements at 25 °C in aqueous solutions of different pH values. The hydrophobic drug dipyridamole was efficiently incorporated into the copolymer aggregates in aqueous solutions of pH 7.40. High partition coefficient values were determined by fluorescence spectroscopy

Well-Defined Cyclic Triblock Terpolymers: A Missing Piece of the Morphology Puzzle

Two well-defined cyclic triblock terpolymers, missing pieces of the terpolymer morphology puzzle, consisting of poly­(isoprene), polystyrene, and poly­(2-vinylpyridine), were synthesized by combining the Glaser coupling reaction with anionic polymerization. An α,ω-dihydroxy linear triblock terpolymer (OH-PI_1,4-<i>b</i>-PS-<i>b</i>-P2VP-OH) was first synthesized followed by transformation of the OH to alkyne groups by esterification with pentynoic acid and cyclization by Glaser coupling. The size exclusion chromatography (SEC) trace of the linear terpolymer precursor was shifted to lower elution time after cyclization, indicating the successful synthesis of the cyclic terpolymer. Additionally, the SEC trace of the cyclic terpolymer produced, after cleavage of the ester groups, shifted again practically to the position corresponding to the linear precursor. The first exploratory results on morphology showed the tremendous influence of the cyclic structure on the morphology of terpolymers