Slow Monomer Addition Research Articles

Quasilinear polyglycidols by triethyborane-controlled anionic polymerization of unprotected glycidol.

In this study, quasilinear polyglycidols (PG)s with ultralow degree of branching (DB) could be synthesized through anionic polymerization of glycidol carried out in the presence of triethylborane (TEB). PGs with DB ≤ 0.10, and molar masses up to 40 kg mol-1 could be indeed obtained using mono- or trifunctional ammonium carboxylates as initiator and under slow monomer addition conditions. The synthesis of degradable PGs through ester linkages obtained by copolymerization of glycidol with anhydride is also described. PG-based amphiphilic di- and triblock quasilinear copolymers were also derived. The role played by TEB is discussed and a polymerization mechanism is proposed.

Facile synthesis of hyperbranched poly(p‐phenyleneethynylene‐alt‐m‐phenyleneethynylene) with narrow dispersity and high branching degree by sonogashira polymerization of an AB2 monomer

ABSTRACTAn AB2 monomer PhBr2CCPhCCH containing one acetylene group and two bromide groups was efficiently synthesized by a strategy based on the different reactivity between aromatic iodide and bromide in Sonogashira reaction. The Sonogashira polymerization of PhBr2CCPhCCH was investigated to get hyperbranched poly(p‐phenyleneethynylene‐alt‐m‐phenyleneethynylene) (hb‐PMPE) in terms of the effects of monomer addition method, core molecule with different functionality, and ratio of [monomer]/[core molecule]. The results showed that narrow dispersities (D) (D: 1.23∼1.50) were obtained by slow monomer addition and with core molecule. Bifunctional core molecule induced narrower dispersity than monofunctional core molecule. The molecular weight of hb‐PMPE increased with increasing ratio of [monomer]/[core molecule], however, a negative deviation from calculated value was observed. The dispersity slightly increased with increasing [monomer]/[core molecule]. When the ratio of [monomer]/[core molecule] was below 50/1, monomodal distribution was observed; whereas when the ratio increased to 70/1, bimodal distribution was obtained. All the polymers showed degrees of branching (DBs) around 0.6. The hb‐PMPEs showed one major absorption band with λmax around 330 nm, and emission band with λmax around 390 nm. All the polymers showed relative quantum yields (Φr) above 0.5 in dilute THF solution. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018, 56, 96–104

Thioether-Bearing Hyperbranched Polyether Polyols with Methionine-Like Side-Chains: A Versatile Platform for Orthogonal Functionalization.

The synthesis of thioether-bearing hyperbranched polyether polyols based on an AB/AB2 type copolymerization (cyclic latent monomers) is introduced. The polymers are prepared by anionic ring-opening multibranching copolymerization of glycidol and 2-(methylthio)ethyl glycidyl ether (MTEGE), which is conveniently accessible in a single etherification step. Slow monomer addition provides control over molecular weights. Moderate dispersities (Đ = 1.48-1.85) are obtained, given the hyperbranched structure. In situ 1 H NMR copolymerization kinetics reveal reactivity ratios of rG = 3.7 and rMTEGE = 0.27. Using slow monomer addition, copolymer composition can be systematically varied, allowing for the adjustment of the hydroxyl/thioether ratio, the degree of branching (DB = 0.36-0.48), thermal properties, and cloud point temperatures in aqueous solution in the range of 29-75 °C. Thioether oxidation to sulfoxides enables to tailor the copolymers' solubility profile. Use of these copolymers as a versatile, multifunctional platform for orthogonal modification is highlighted. The methyl sulfide groups can be selectively alkoxylated, using propylene oxide, allyl glycidyl ether, or furfuryl glycidyl ether, resulting in functional hyperbranched polyelectrolytes. Reaction of the alcohol groups with benzyl isocyanate demonstrates successful orthogonal functionalization.

Hyperbranched Polymers with High Degrees of Branching and Low Dispersity Values: Pushing the Limits of Thiol–Yne Chemistry

We propose a versatile approach to the production of hyperbranched polymers with high degrees of branching and low dispersity values (Đ), involving slow monomer addition of a thiol/yne monomer to multifunctional core molecules in the presence of photoinitiator and under UV irradiation. The small thiol/yne monomer was synthesized via 1-ethyl-3-(3-(dimethylamino)propyl)carbodiimide hydrochloride (EDC·HCl) esterification, and batch polymerizations were performed at varying concentrations. The batch thiol–yne polymerizations had fast reaction kinetics and large dispersity values that increased with increasing concentration. Introduction of monomer by slow addition to a multifunctional alkyne core (tri(prop-2-yn-1-yl) 1,3,5-benzenetricarboxylate) or alkene core (triallyl 1,3,5-benzenetricarboxylate) was found to lower dispersity at monomer concentrations of 0.5–2.0 M. Degrees of branching were determined by 1H NMR spectroscopy to be greater than 0.8 in most cases. Increasing the fraction of core molecule was f...

Design a Highly Reactive Trifunctional Core Molecule To Obtain Hyperbranched Polymers with over a Million Molecular Weight in One-Pot Click Polymerization

We present the first one-pot one-batch synthesis of hyperbranched polymers with over a million molecular weight and low polydispersity in the copper-catalyzed alkyne–azide cycloaddition (CuAAC) polymerization of AB2 monomer. In contrast to the traditional triazido core molecule that failed to produce high molecular weight polymer, a novel tris-triazoleamine-based B3 molecule was designed, which complexed with CuI catalyst and activated the azido reactivity in both B3 and B3-containing polymers. The polymerization demonstrated linear increase of polymer molecular weights with the feed ratio of [AB2]0:[B3]0 with no need of slow monomer addition. At the same time, a higher ratio of [CuI]0:[B3]0 showed no influence on molecular weight but significantly increased the polymerization rate and produced hyperbranched polymers with higher degree of branching. The one-pot polymerization using [AB2]0:[B3]0:[Cu]0 = 2700:1:10 produced hyperbranched polymers with molecular weight Mn = 1.01 × 106 and polydispersity Mw/Mn...

Hyperbranched Polyols via Copolymerization of 1,2-Butylene Oxide and Glycidol: Comparison of Batch Synthesis and Slow Monomer Addition

Hyperbranched poly(butylene oxide) polyols have been synthesized by multibranching anionic ring-opening copolymerization of 1,2-butylene oxide and glycidol. Systematic variation of the composition from 24 to 74% glycidol content resulted in a series of moderately distributed copolymers (Đ = 1.41–1.65, SEC), albeit with limited molecular weights in the solvent-free batch process in the range of 900–1300 g mol–1 (apparent Mn determined by SEC with PEG standards). In situ monitoring of the copolymerization kinetics by 1H NMR showed a pronounced compositional drift with respect to the monomer feed, indicating a strongly tapered microstructure caused by the higher reactivity of glycidol. In the case of slow monomer addition considerably higher apparent molecular weights up to 8500 g mol–1 were obtained (SEC). By alteration of the comonomer ratio, aqueous solubility of the hyperbranched copolymers could be tailored, resulting in well-defined cloud points between 20 and 84 °C. Glass transition temperatures betwe...

Statistical properties of linear-hyperbranched graft copolymers prepared via "hypergrafting" of AB(m) monomers from linear B-functional core chains: A molecular dynamics simulation.

The reaction of ABm monomers (m = 2, 3) with a multifunctional Bf-type polymer chain ("hypergrafting") is studied by coarse-grained molecular dynamics simulations. The ABm monomers are hypergrafted using the slow monomer addition strategy. Fully dendronized, i.e., perfectly branched polymers are also simulated for comparison. The degree of branching of the molecules obtained with the "hypergrafting" process critically depends on the rate with which monomers attach to inner monomers compared to terminal monomers. This ratio is more favorable if the ABm monomers have lower reactivity, since the free monomers then have time to diffuse inside the chain. Configurational chain properties are also determined, showing that the stretching of the polymer backbone as a consequence of the "hypergrafting" procedure is much less pronounced than for perfectly dendronized chains. Furthermore, we analyze the scaling of various quantities with molecular weight M for large M (M > 100). The Wiener index scales as M(2.3), which is intermediate between linear chains (M(3)) and perfectly branched polymers (M(2)ln(M)). The polymer size, characterized by the radius of gyration Rg or the hydrodynamic radius Rh, is found to scale as Rg,h ∝ M(ν) with ν ≈ 0.38, which lies between the exponent of diffusion limited aggregation (ν = 0.4) and the mean-field exponent predicted by Konkolewicz and co-workers [Phys. Rev. Lett. 98, 238301 (2007)] (ν = 0.33).

Dispersity control of linear poly(glycidyl ether)s by slow monomer addition

In this communication we demonstrate that the extent of dispersity of poly(allyl glycidyl ether) and poly(ethoxy ethyl glycidyl ether) can be reduced by slow monomer addition with potassium tert-butoxide as initiator and THF as solvent at 45 °C.

Synthesis of amphiphilic linear-hyperbranched graft-copolymers via grafting based on linear polyethylene backbone

The synthesis of amphiphilic linear-hyperbranched graft-copolymers in a grafting-from approach is reported. The linear polyethylene with terminated hydroxyls, prepared by copolymerization of ethylene and 10-undecen-1-ol, was used as macroinitiator for ring-opening multibranching polymerization of glycidol by a typical slow monomer addition approach. Successful attachment of the hyperbranched grafts to the linear polyethylene backbone was confirmed by 1H/13C NMR, GPC, and TGA. The degree of polymerization and Mw/Mn of hyperbranched grafts were efficiently controlled by temperature, deprotonation ratio as well as the molar ratio of glycidol/hydroxyl (Nglycidol/NOH). The complicated microstructures caused by unsymmetric glycidol structure were analyzed by DEPT and 2D HSQC spectra, the degree of branching of 0.63–0.66 were calculated, indicating the extent of branch is close to theoretical values. The thermal analysis of linear-hyperbranched copolymers via TGA and DSC is also presented. To our knowledge, this is the first report of a linear-hyperbranched graft-copolymer with a crystalline and nonpolar linear-polyethylene segment. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014, 52, 2146–2154

Anionic Ring-Opening Polymerization Simulations for Hyperbranched Polyglycerols with Defined Molecular Weights

We have investigated the anionic ring-opening multibranching polymerization for hyperbranched polyglycerol using slow monomer addition at 120 °C. Different molecular masses were targeted, and the reaction mixture was probed at regular intervals for the experimental data. The resulting polymers were characterized by gel permeation chromatography, mass spectrometry, and NMR spectroscopy. A computational PREDICI model of the polymerization was developed to describe the experimental parameter dependencies. The rate coefficients were determined for the thermal and base-catalyzed, intra- and intermolecular reactions by fitting simulated number- and weight-average molecular weights to the experimental values. Although the main reaction was expected to be base-mediated, thermal propagation proved to play a crucial role in the dynamics of the investigated system. Both thermal and base-catalyzed self-initiation significantly increased the dispersity for targeting molecular masses exceeding 10 kDa, whereby the size of the growing polymer species was affected by polymerization kinetics.

Polydispersity and Molecular Weight Distribution of Hyperbranched Graft Copolymers via “Hypergrafting” of ABm Monomers from Polydisperse Macroinitiator Cores: Theory Meets Synthesis

The hypergrafting strategy designates the synthesis of hyperbranched graft copolymers (HGCs) in a grafting-from approach, using ABm monomers, from multifunctional, polydisperse macroinitiator cores by slow monomer addition. Hypergrafting leads to complex polymer topologies with defined molecular weight, degree of branching (DB), and polydispersity (PD). By a generating function formalism, a generally applicable equation for the PD of HGCs (PD = PDf + (m – 1)/f) is derived, where PDf is the polydispersity of the core and f its average functionality. In addition, the complete molecular weight distribution function has been calculated for varied m and f as well as for a given distribution of initiator functionalities f. For comparison of the theoretical predictions with experimental results, a series of novel linear polyglycerol-graft-hyperbranched polyglycerol (linPG-g-hbPG) HGCs (Mn = 1000–4000 g mol–1) were synthesized and characterized as a model system. An increase in polydispersity occurred as a con...

Kinetic Model of Semibatch Polymerization with ABg Monomer and Bƒ Core

The kinetics of semibatch polymerization (i.e. slow monomer addition) with ABg monomer and Bf core was developed. The analytical expressions of molecular parameters, such as the molecular size distribution function, the average degree of polymerization and polydispersity index, were derived, which dependent on the structure of monomer and core molecule used. The molecular parameters are adjustable by selecting suitable core functionality (f), monomer functionality (g) and core/monomer ratio (α). Comparison with the batch (one-pot) polymerization indicates that the semibatch polymerization can extremely narrow the molecular weight distribution for the products made of ABgmonomer and Bf core.

Suzuki Polycondensation toward High Molecular Weight Poly(m-phenylene)s: Mechanistic Insights and End-Functionalization

Synthesis of a poly(m-phenylene) by Suzuki polycondensation (SPC) using an AB-type m-phenylene monomer is reported (A and B refer to bromo and boron functional groups, respectively). Despite the attempted high molecular weight products, SPC under the conventional conditions using Pd[P(p-Tol)3]3 as catalyst gave rise to oligomeric products only. They comprise cycles and several series of open-chain poly(m-phenylene)s with various end group patterns. These patterns were caused by side reactions such as ligand scrambling. Buchwald’s SPhos ligand was therefore alternatively employed for high turnover catalysis to accelerate SPC over such detrimental side reactions. This modification indeed led to the formation of high molecular weight products ∼40 kDa (DP ∼ 210), while oligomeric cyclic products still remained prominent. Cycle formation could, however, drastically be reduced by slow monomer addition. SPC was also performed in the presence of an excess monofunctional compound, R–A or R–B. The molecular weights...

Synthesis of Hyperbranched Polymer Using Slow Monomer Addition Method

This paper details the synthesis of a well-defined hyperbranched polymer using a slow monomer addition method. The polymerization under slow monomer addition conditions results in a very low monomer concentration actually present in the reaction mixture, and the exclusive reaction of the monomer with the growing polyfunctional macromolecules occurs, resulting in a high molecular weight and a high degree of branching value. Thus, the slow monomer addition is a versatile and preferential method for the controlled synthesis of a well-defined hyperbranched polymer with both a high molecular weight and a high degree of branching value.

Synthesis of novel hyperbranched polymer through cationic ring-opening multibranching polymerization of 2-hydroxymethyloxetane

The cationic ring-opening multibranching polymerization of 2-hydroxymethyloxetane (1) as a novel latent AB2-type monomer was carried out using trifluoromethane sulfonic acid or trifluoroboron diethyl etherate by a slow-monomer-addition (SMA) method. The polymer yield of poly-1 ranged from ca. 58–88%, which increase with the increasing monomer addition time on the SMA method. The absolute molecular weights (Mw,MALLS) and the polydispersities of poly-1 were in the range of 8,000–43,500 and 1.45–4.53, respectively, which also increased with the increasing monomer addition time. The Mark-Houwink-Sakurada exponents α in 0.2 M NaNO3 aq. were determined to be 0.02–0.25 for poly-1, indicating that poly-1 has compact forms in the solution because of the highly branched structure. The degree of the branching value of poly-1, which was calculated by Frey's equation, ranged from ca. 0.50 to 0.58, which increased with the increasing monomer addition time. The steady shear flow of poly-1 in aqueous solution exhibited a Newtonian behavior with steady shear viscosities independent of the shear rate. The results of the MALLS, NMR, and viscosity measurements indicated that poly-1 is composed of a highly branched structure, i.e., the hyperbranched poly (2-hydroxymethyloxetane). © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011

Diffusion-limited hyperbranched polymers with substitution effect

Highly branched structure has the essential influence on macromolecular property and functionality in physics and chemistry. In this work, we proposed a diffusion-limited reaction model with the consideration of macromolecular unit relaxations and substitution effect of monomers to study the structure of hyperbranched polymers prepared by slow monomer addition to a core molecule. The exponential relationship (R(g) ∼ N(λ)) between the radius of gyration R(g) and the degree of polymerization N, was systematically analyzed at various branching degrees. It is shown that the effective exponent λ(eff) decreases at lower N and but increases toward that of diffusion-limited aggregation (DLA) clusters (λ(DLA) = 0.4) with the degree of polymerization increasing. The substitution effect of monomers in reaction strongly influences the evolution pathway of λ(eff). With the static light scattering technique, the fractal property of internal chains was further calculated. A general law about the radial distribution of the units of diffusion-limited hyperbranched polymers was found that, at smaller reactivity ratio k(12), the radial density of all monomer units D(A) declines from the center region to the peripheral layer revealing the dense core structure; however, at larger k(12), the density distribution shows a loose-dense-loose structure. These structural characteristics are helpful to deeply understand the property of hyperbranched polymers.

Synthesis of hyperbranched polyester‐amides and their application as crosslinkers for polyurethane curing systems

AbstractA series of hyperbranched polyester‐amides (S1, S2, S3) with trimethylolpropane as a core molecule were synthesized using core‐dilution/slow monomer addition strategy. The products were characterized by FTIR, 13C NMR, GPC, TGA, hydroxyl value measurement, and viscosity measurement. The result showed that the hyperbranched polyester‐amides synthesized had narrow molecular weight distribution and high degree of branching (DB). The hyperbranched polyester‐amides synthesized were used as crosslinkers for polyurethane curing systems and the mechanical properties of the polyurethane curing systems were investigated. It was found that the best tensile property and tear strength were obtained when the S2 were used as crosslinkers and the molar ratio of OH and NCO was 1 : 1. It was also found that the polyurethane curing systems had the highest hardness and Tg when the S3 were used as crosslinkers. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Effect of slow monomer addition on molecular parameters of hyperbranched polymers synthesized in the presence of multifunctional core molecules

This study develops the kinetics for the slow monomer addition technique in the synthesis of hyperbranched polymers. Taking the conversion of monomer (x) as a variable, we derived the analytic expressions of molecular size distribution function, average degree of polymerization, polydispersity index and degree of branching. These expressions are not only amenable to the polymerization with high monomer conversion, but also appropriate to describe the whole polymerization process. Comparison with the one-pot polymerization indicates that the slow monomer addition technique improves the molecular weight distribution and increases the degree of branching for the products obtained.

Electroactive Linear–Hyperbranched Block Copolymers Based on Linear Poly(ferrocenylsilane)s and Hyperbranched Poly(carbosilane)s

A convenient two-step protocol is presented for synthesis of linear-hyperbranched diblock copolymers consisting of a linear, organometallic poly(ferrocenylsilane) (PFS) block and hyperbranched poly(carbosilane) (hbPCS) segments. Linear PFS diblock copolymers were synthesized through photolytic ring-opening polymerization of dimethyl[1]silaferrocenophane as the first block and methylvinyl[1]silaferrocenophane as the second. These block copolymers served as polyfunctional cores in a subsequent hydrosilylation polyaddition of different silane-based AB(2) monomers. Three AB(2) monomers (methyldiallylsilane; methyldiundecenylsilane, and ferrocenyldiallylsilane) were investigated; they introduced structural diversity to the hyperbranched block and showed variable reactivity for the hydrosilylation reaction. In the case with the additional ferrocene moiety in the ferrocenyldiallylsilane monomer, an electroactive hyperbranched block was generated. No slow monomer addition was necessary for molecular-weight control of the hyperbranching polyaddition, as the core had much higher functionality and reactivity than the carbosilane monomers. Different block ratios were targeted and hybrid block copolymers with narrow polydispersity (<1.2) were obtained. All the resulting polymers were investigated and characterized by size exclusion chromatography, NMR spectroscopy, cyclic voltammetry, and TEM, and exhibited strongly anisotropic aggregation.

Amphiphilic Linear-Hyperbranched Block Copolymers with Linear Poly(ethylene oxide) and Hyperbranched Poly(carbosilane) Block

The synthesis of amphiphilic linear-hyperbranched block copolymers with a linear poly(ethylene oxide) (PEO) segment and a hyperbranched poly(carbosilane)s (PCS) block in a rapid three-step strategy is described, combining oxyanionic polymerization with carbosilane chemistry. A linear precursor block copolymer was synthesized via anionic polymerization of allyl glycidyl ether onto a commercial hydroxyl-terminated PEO, using its cesium alkoxide as macro-initiator. The resulting linear AB or ABA-type di- or triblock copolymers serve as polymer cores for the subsequent hydrosilylation polyaddition of an AB2-type carbosilane monomer. Di(allyl)methylsilane or methyldi(undec-10-enylsilane) were employed, using Karstedt’s catalyst as Pt0-species. Due to the high reactivity of allyloxy groups in catalytic hydrosilylation reactions, the slow monomer addition technique, previously used for the controlled polyaddition of AB2-monomers, was not necessary in this case and complete conversion of all core allyl groups is ...