Self-condensing Vinyl Copolymerization Research Articles

One-Pot Structure-Controlled Synthesis of Hyperbranched Polymers by a "Latent" Inimer Strategy Based on Diels-Alder Chemistry.

An efficient "one-pot" strategy for the structure-controlled synthesis of hyperbranched polymers (HBPs) based on a "latent" inimer (LI-Br), containing a furan-protected maleimide monomer and a haloalkane initiator, is presented. At high temperatures, the "latent" inimer is converted to a "real" inimer after releasing maleimide (MI) via a retro-Diels-Alder (r-DA) reaction and then copolymerized with methyl methacrylate by self-condensing vinyl copolymerization. Due to the dynamic characteristic of the r-DA reaction, the release of naked MI and the subsequent copolymerization can be regulated by the temperature or stereochemistry of Diels-Alder (DA) adducts. Thus, the "one-pot" structure-controlled synthesis of HBPs with various degrees of branching was achieved. By further implementation of a programmable temperature change, some valuable hyperbranched topologies such as star-shaped and long-chain hyperbranched polymers can be constructed avoiding sophisticated synthetic routes.

Hyperbranched and Hyperstar Polybutadienes via Anionic Self-Condensing Vinyl Copolymerization

Hyperbranched and Hyperstar Polybutadienes via Anionic Self-Condensing Vinyl Copolymerization

Visible light induced one-pot synthesis of amphiphilic hyperbranched copolymers

Dimanganese decacarbonyl (Mn2(CO)10) and alkyl halide combination has unique visible light radical generating property which is useful in the fabrication of many complex macromolecular structures. Herein, we present a generic simple and rapid synthetic approach for the preparation amphiphilic hyperbranched macromolecular structures with controlled branching density and hydrophilicity. The method is based on the visible light induced self-condensing vinyl copolymerization of methyl methacrylate (MMA), 2-(2-bromoisobutryloxy)ethyl methacrylate (BIBEM) and poly(ethylene glycol) methyl ether methacrylate as monomer, inimer and hydrophilic comonomer, respectively, in the presence of Mn2(CO)10. The resulting polymers possess both hydrophobic and hydrophilic sequences offering many potential bio applications such as controlled drug delivery and release. Moreover, the resulting polymers contain also unreacted bromide groups in the final structure which allow postfunctionalization through copper(I)-catalyzed alkyne-azide cycloaddition “click” reactions.

Predicting Average Molecular Weights and Branching Level for Self‐Condensing Vinyl Copolymerization in a CSTR

AbstractA continuous stirred‐tank reactor (CSTR) model is developed to produce arborescent polyisobutylene via carbocationic copolymerization of isobutylene and inimer using multidimensional method of moments. The model is used to predict dynamic changes in average branching level (Bkin) and number‐average and weight‐average molecular weights (). Simulations of this self‐condensing vinyl copolymerization (SCVCP) show a tendency toward higher polydispersity and higher Bkin compared to batch reactor simulations conducted using the same recipes and residence times. At high inimer feed concentration and/or long residence time, the model predicts that a CSTR does not reach steady‐state operation due to increasing toward infinity. There is a narrow operating range in which inimer feed concentrations can be adjusted to achieve a desired steady‐state . If SCVCP is to be conducted in a CSTR, it will be important to ensure that residence times and inimer feed concentrations are selected within the stable operating window.

Recent Progress on Hyperbranched Polymers Synthesized via Radical-Based Self-Condensing Vinyl Polymerization.

This short review article summarizes recent reports on using controlled radical polymerization (CRP) of inimers (compounds containing initiating group and vinyl group in one molecule) or transmers (compounds containing chain transfer group and vinyl group in one molecule) for the synthesis of hyperbranched polymers. These inimers and transmers that carry numerous functional groups could be homopolymerized, i.e., self-condensing vinyl polymerization, or copolymerized with monovinyl monomers, i.e., self-condensing vinyl copolymerization, using atom transfer radical polymerization (ATRP), nitroxide-mediated polymerization (NMP) or reversible addition fragmentation chain transfer (RAFT) polymerization techniques, producing hyperbranched polymers and hyperstar polymers with tunable molecular weights, compositions and degree of branching. Recent reports that attempted different strategies to regulate polymer–polymer reactions were introduced, demonstrating possible syntheses of hyperbranched polymers with better defined structures and relatively low molecular weight dispersity. Finally, several CRP-produced hyperbranched polymers were discussed on their applications for encapsulation of guest molecules, nanomedicine, diagnostic imaging and catalysis.

Biocompatible Reduction and pH Dual-Responsive Core Cross-Linked Micelles Based on Multifunctional Amphiphilic Linear-Hyperbranched Copolymer for Controlled Anticancer Drug Delivery.

Novel strategy has been developed for fabricating the biocompatible reduction and pH dual-responsive core cross-linked (CCL) micelles as drug delivery system (DDS) for the controlled anticancer drug delivery, via the atom transfer radical polymerization (ATRP) of tert-butyl acrylate (tBA) with N,N'-bis(acryloyl)cystamine (BACy) as cross-linker and a multifunctional amphiphilic linear-hyperbranched copolymer as macroinitiator, which was synthesized via the self-condensing vinyl copolymerization (SCVCP) of tBA and p-chloromethylstyrene (CMS) with a poly(ethylene glycol) (PEG) based initiator (mPEG-Br). The hydrolyzed core cross-linked (HCCL) micelles were obtained as DDS for doxorubicin (DOX) by hydrolysis the tBA units into acrylic acid (AA) ones. The in vitro release performance showed that higher GSH concentration and/or lower pH value would lead to a faster and more efficient DOX release, meaning their reduction and pH dual-responsiveness. Therefore, the proposed HCCL micelles are expected to be potential anticancer drug-carriers for tumor microenvironment responsive controlled delivery.

Effect of branching architecture on glass transition behavior of hyperbranched copolystyrenes: the experiment and simulation studies

By controlling the feed ratio of CMS/styrene and the polymerization time, a series of hyperbranched copolystyrenes (HBCPS) were synthesized with comparable weight-averaged molecular weights (M w) but different degree of branching (DB) through atom transfer radical self-condensing vinyl copolymerization (ATR-SCVCP) with CuBr/2,2′-bipyridyl as the catalyst. The resulting HBCPS samples were used to investigate the effect of branching architecture on their glass transition behavior. With the DB increased, the glass transition temperatures (T g) of HBCPS samples measured by DMA and DSC both decreased. Their spin-lattice relaxation times (1H T 1r) of protons displayed the same downtrend with increasing DB. Besides, a correlation between the T gs and the DB was well established by all-atom molecular dynamics (MD) simulations. The values of MD-determined T gs are little higher than the corresponding experimental ones. However, the dependence of T gs on DB is in good agreement with the experimental results, i.e., T g decreases both in experiments and simulations with increasing DB.

Disulfide-Functionalized Unimolecular Micelles as Selective Redox-Responsive Nanocarriers.

Redox-sensitive hyperbranched dendritic-linear polymers (HBDLPs) were prepared and stabilized individually as unimolecular micelles with diameters in the range 25-40 nm. The high molecular weight (500-950 kDa), core-shell amphiphilic structures were synthesized through a combination of self-condensing vinyl copolymerization (SCVCP) and atom transfer radical polymerization (ATRP). Cleavable disulfide bonds were introduced, either in the backbone, or in pendant groups, of the hyperbranched core of the HBDLPs. By triggered reductive degradation, the HBDLPs showed up to a 7-fold decrease in molecular weight, and the extent of degradation was tuned by the amount of incorporated disulfides. The HBDLP with pendant disulfide-linked functionalities in the hyperbranched core was readily postfunctionalized with a hydrophobic dye, as a mimic for a drug. An instant release of the dye was observed as a response to a reductive environment similar to the one present intracellularly. The proposed strategy shows a facile route to highly stable unimolecular micelles, which attractively exhibit redox-responsive degradation and cargo release properties.

Segmented Highly Branched Copolymers: Rationally Designed Macromolecules for Improved and Tunable (19)F MRI.

Highly branched polymers are a promising platform for the design of next-generation contrast agents for (19)F magnetic resonance imaging (MRI). A series of segmented highly branched polymers (SHBPs) consisting of fluoro- and PEG-based monomers were synthesized by self-condensing vinyl copolymerization (SCVP) using the reversible addition-fragmentation chain transfer (RAFT) technique. SHBPs having different compositions and degrees of branching were obtained by varying the monomer type and feed ratio of monomer to chain transfer agent (CTA). The chemical structures and physical properties of the branched polymers were thoroughly characterized in detail by NMR, SEC and DSC. The systematic variation in structural parameters allowed the relationships between molecular structure, sequence distribution, and imaging performance to be examined. The (19)F NMR properties were strongly affected by the sequence distribution of the fluorinated monomers, the type of polymer backbone and the degree of branching. As a result, SHBPs consisting of statistical copolymeric segments of acrylate units were identified as excellent candidates for imaging due to a single (19)F signal, long T2 relaxation times, and high fluorine contents. The SHBPs could be all imaged or selectively imaged by taking advantage of the differences in relaxation times, demonstrating tunable and selective imaging performance through tailoring the structure and composition of the SHBPs.

Effect of feed rate of monofunctional monomers on structure of hyperbranched copolymers formed by self-condensing vinyl copolymerization in semibatch reactor

Hyperbranched polymers (HBPs) formed by a self-condensing vinyl copolymerization, SCVCP, of monofunctional monomers M gradually fed into a reactor containing inimers AB*, which had been charged initially, were investigated using a kinetic model. Under the assumption that no cyclization occurred during polymerization, changes in the average degree of polymerization (DP), the degree-of-polymerization dispersity, the degree of branching (DB), and the number of structural units in the hyperbranched copolymers at different feed rates of monomers M were calculated by a generating function method. The distribution of the degree of polymerization could be narrowed with the addition of monomers M, and the degree-of-polymerization dispersity was increased slightly at a slower feed rate parameter of M, ϕ. A higher DB of the HBPs could be obtained at a slower feed rate and a specific stopping ratio of M, θ. For instance, a final DB of approximately 0.62 was attained at ϕ=0.2 and θ=1.2, which was higher than the maximum DB of 0.5 attained in a batch system with monomers M at θ=0.6.

Coil Flow Inversion as a Route To Control Polymerization in Microreactors

Linear and branched polymers of 2-(dimethylamino)ethyl methacrylate (PDMAEMA) were synthesized in flow by atom transfer radical polymerization (ATRP) and self-condensing vinyl copolymerization adapted to ATRP, respectively, in capillary type stainless steel coiled tube (CT) microreactors. Coil flow inversion (CFI) was introduced to achieve better mixing and narrower residence time distributions during polymerization. This strategy was adopted to improve control over macromolecular characteristics and polymer architecture. Polydispersity index (PDI), as an overall indicator of control over polymerization, was significantly lower for CFI in the case of linear PDMAEMA, 1.39 compared to 1.53 for CT. For branched polymers containing up to 10 mol % of inimer, a reduced PDI was also obtained for CFI microreactor. As for the branching efficiency, it was found to follow the following trend CFI > CT > batch reactor.

Hyperbranched polymers and dendrimers as templates for organic/inorganic hybrid nanomaterials.

This paper reviews the recent research and development of hyperbranched polymers (HPs) and dendrimers, and their use as templates for organic-inorganic hybrid nanomaterials. Hyperbranched polymers (HPs) are highly branched macromolecules with three-dimensional globular structures featuring unique properties such as low viscosity, high solubility, and a large number of terminal functional groups compared to their linear analogs. They are easily prepared by (1) condensation polymerization, (2) self-condensing vinyl copolymerization (SCVCP), and (3) ring-opening multibranch polymerization methods. Organic-inorganic hybrid nanomaterials are synthesized by a template approach using HPs/dendrimers. Monometallic, bimetallic (alloy and core/shell), semiconductor, and metal oxide nanoparticles have been prepared by this route. The dendrimer component of these composites serves not only as a template for preparing the nanoparticles but also as a stabilizer for the nanoparticles.

Thermally-labile segmented hyperbranched copolymers: using reversible-covalent chemistry to investigate the mechanism of self-condensing vinyl copolymerization

A thermally-reversible inimer was used to confirm the controlled growth of individual branches during self-condensing vinyl atom transfer radical polymerization (ATRP).

Monte Carlo Model for Arborescent Polyisobutylene Production in the Batch Reactor

A Monte Carlo (MC) model is developed to predict molecular weight distribution and branching during the production of arborescent polyisobutylene. The model describes self‐condensing vinyl copolymerization (SCVCP) of isobutylene and inimer via living carbocationic polymerization. Six different propagation rate constants are required to account for two types of vinyl groups and three types of carbocations in the system. MC model predictions are better than predictions from a previous PREDICI material balance model because fewer simplifying assumptions are required. The MC model predictions reveal that reactions that were previously neglected have an important influence on polymer properties.

Dendritic Block and Dendritic Brush Copolymers through Anionic Macroinimer Approach

Anionic macroinimer is prepared through selective monoaddition of polyisoprenyllithium (PILi) toward 1,3-bis(1-phenylvinyl)benzene (MDDPE) in THF/cyclohexane mixture. The resulting macroinimer, possessing a living anion and a diphenylethylene (DPE) group at the same end of the PI chain, undergoes self-condensing vinyl copolymerization (SCVCP) with styrene after the solvent has been switched from mixture of THF/cyclohexane into pure cyclohexane. Dendritic block copolymers of styrene and isoprene are obtained, in which PI chains are linked to the branch points. The molecular weights of the dendritic products mainly depend on the ratio of monomer to macroinimer, whereas PI chain length has only slight effects. The PI segments are subsequently epoxidized and grafted with PILi or polystyrenyllithium (PSLi) to give dendritic polymer brushes. Both dendritic block copolymers and dendritic polymer brushes show decreased intrinsic viscosities. Dendritic block copolymer of styrene and isoprene undergoes a specially slow process of self-assembly, from unimolecular micelles and intermediate compound micelles to large compound micelles, in mixed solvent (n-heptane/THF = 19/1, v/v). In addition, conversion of large compound micelles into lamellar structure is observed for the first time in self-assembly of dendritically branched polymers.

Synthesis, Characterization, and Flocculation Properties of Branched Cationic Polyacrylamide

A water soluble branched cationic polyacrylamide (BCPAM) was synthesized using solution polymerization. The polymerization was initiated using potassium diperiodatocuprate, K5[Cu(HIO6)2](Cu(III)), initiating the self-condensing vinyl copolymerization of acrylamide and acryloxyethyltrimethyl ammonium chloride (DAC) monomer. The resulting copolymer was characterized by the use of Fourier-transform infrared (FTIR) spectroscopy and nuclear magnetic resonance (NMR) spectroscopy. Its flocculation properties were evaluated with standard jar tests of sewage. The effects of initiator concentration, monomer concentration, reaction temperature, and the mass ratio of monomers on intrinsic viscosity and flocculation properties of the product were determined using single-factor experiments and orthogonal experiment.

A Pd–diimine catalytic inimer for synthesis of polyethylenes of hyperbranched-on-hyperbranched and star architectures

A Pd-diimine catalytic inimer containing uniquely catalytic, initiating, and monomeric functionalities in one catalyst molecule is designed. It enables the first self-condensing vinyl copolymerization of ethylene, leading to polyethylenes of a hyperbranched-on-hyperbranched architecture. Meanwhile, it also facilitates the synthesis of star polyethylenes by tandem UV-coordinative polymerization.

Water-Soluble and Clickable Segmented Hyperbranched Polymers for Multifunctionalization and Novel Architecture Construction

A series of novel and narrowly polydispersed regular chain-segmented hyperbranched poly(tertiary amino methacrylate)s (HPTAM)s with hydrophilic core and hydrophobic shell were synthesized via the combination of self-condensing vinyl copolymerization (SCVCP) and reversible addition–fragmentation chain transfer (RAFT) methodology. 2-(Dimethylamino)ethyl methacrylate (DMAEMA) and 2-((2-(((dodecylthio)carbonothioyl)thio)-2-methylpropanoyl)oxy)ethyl acrylate (ACDT) at various molar feed ratios (γ, [DMAEMA]:[ACDT]) were chosen as monomers for linear segment formation of the structure. The copolymerization kinetics revealed that during the polymerization the real-time γ value kept almost constant and was consistent with the initial feed ratio. So HPTAMs possesses regular linear chains between every two neighboring branching units, which closely resemble HyperMacs in structure. Fast click-like Menschutkin reaction (i.e., quaternarization) of the segmented hyperbranched polymers with propargyl bromide and 2-azidoe...

Mechanistic study of Atom Transfer Radical Polymerization in the Presence of an Inimer: Toward Highly Branched Controlled Macromolecular Architectures through One-Pot Reaction

Highly branched polymethacrylates have recently offered new perspectives in lithographic performance and drug delivery. The control of branching remains yet challenging and requires fundamental investigation to consider new applications. Therefore, an advanced study of the formation mechanism of branched polymers synthesized by self-condensing vinyl copolymerization (SCVCP) of a methacrylic AB* inimer, 2-(2-bromoisobutyryloxy)ethyl methacrylate (BIEM), with methyl methacrylate (MMA) via atom transfer radical polymerization (ATRP) has been performed. Evidence of branched structures was obtained with a conventional GPC apparatus equipped with a multiangle light scattering detector and detailed 1H NMR analyses. A three-step reaction scheme is suggested according to the dependence of molecular weight with conversion. Controlled radical polymerization mainly occurs until moderate conversions, with the participation of inimer as chain initiator. Then the polymerization of small macromolecules, through consumpti...

Hyperbranched Glycopolymer Grafted Microspheres

The synthesis and characterization of acetylglucosamine-displaying microspheres consisting of poly(divinylbenzene) (PDVB) cores onto which chains of linear and branched glycopolymer chains were grafted via atom transfer radical polymerization (ATRP) and self-condensing vinyl copolymerization (SCVCP), respectively, are reported. PDVB particles with a diameter of 1.5 μm exhibit a layer of lightly cross-linked PDVB in the periphery of the particle and therefore enable a “grafting through” approach due to the residual vinyl groups on the surface. The incorporation of the hydrophobic initiator−monomer (inimer) 2-(2-bromoisobutyryloxy)ethyl methacrylate (BIEM) led to compact and branched structures in the shell of the core−shell particles, whereas the ratio of BIEM to 1-methacryloyloxyethyl 2-acetamido-2-deoxy-3,4,6-triacetylglucopyranoside (tetAcGlc) affected the surface coverage. Lectin-binding experiments indicated a strong affinity of wheat germ agglutinin (WGA), a glucosamine-specific lectin, toward the hy...