AB2 Monomer Research Articles

Macromol. Rapid Commun. 5/2017

Front Cover: Controlled supramolecular architecture transformation from supramolecular hyperbranched homopolymer to alternating copolymer was successfully achieved by “competitive self-sorting” assembly. The supramolecular hyperbranched homopolymer was initially constructed by the self-assembly of dialkylammonium salt (DAAS)-functionalized pillar[5]arene (MeP5) AB2 monomers. After adding CD2 monomer to the AB2 system, the initial supramolecular hyperbranched homopolymer was disrupted and then reassembled into a new supramolecular hyperbranched alternating copolymer. Further information can be found in article 1600631, by H. Li, X. D. Fan,* X. Min, Y. C. Qian, and W. Tian*.

Synthesis of polymeric ionic liquids with unidirectional chain topology by AB step growth polymerization

Poly(ionic liquid)s with alkyl imidazolium moieties in the main chain were synthesized by step growth addition polymerization of the AB monomers 1-(4-chlorobutyl)-1H-imidazole, 1-(6-chlorohexyl)-1H-imidazole, and 1-(6-bromohexyl)-1H-imidazole in the melt. The molar masses of the polymers were controlled by adding 1-butyl-1H-imidazole as monofunctional chain stopper. The bromine containing monomer polymerized spontaneously at room temperature whereas the chlorine containing monomers were sufficiently stable up to 40 °C. This could be evidenced by DSC measurements which showed a broad exothermal peak above 40 °C caused by the polymerization. MALDI-TOF investigations proved that dissociation of the alkyl imidazolium groups which might disturb the expected directional chain topology (AB-AB-AB…) did not occur. This is an important precondition for the intended cross-linking free grafting reactions of the AB monomers on halide containing polymers without any danger of gelation. Additionally, the results of the MALDI-TOF investigations indicated partial complexation of the polymer with the matrix and structural rearrangements during the measurements which converted the ionic imidazolium moieties into neutral moieties. The thermal behavior of the poly(ionic liquid)s has proved to be dependent on the length of the alkyl linking group between the imidazolium moieties and the type of counter ion.

A Novel Chain-Growth CuAAC Polymerization: One-pot Synthesis of Dendritic Hyperbranched Polymers with Well-Defined Structures

This highlight presents an overview of our recent achievements on developing a chain-growth copper-catalyzed azide–alkyne cycloaddition (CuAAC) polymerization of multifunctional ABm (m ≥ 2) monomers to produce structurally defined hyperbranched polymers in one pot. The chain-growth mechanism is attributed to the dedicate complexation between copper(I) catalyst and triazole groups that confine the copper catalyst in the polymers and selectively favor the polymer–monomer reaction rather than the monomer–monomer reactions. The living nature of this CuAAC polymerization was extensively explored to demonstrate the intriguing features of multibatch addition of various AB2 monomers to produce hyperbranched polymers with high molar mass, low dispersity, core-shell segmented structures, and tunable solubility. 1 Background 2 Development of Living Chain-Growth CuAAC Polymerization 3 Functionalization and Segmented Structure in Hyperbranched Polymers 4 Conclusion

Condensation polymerization of AB2 monomers – modeling and validation of model of polyreaction performed at the room temperature

Condensation polymerization of AB2 monomers – modeling and validation of model of polyreaction performed at the room temperature

New biosourced AA and AB monomers from 1,4:3,6-dianhydrohexitols, Isosorbide, Isomannide, and Isoidide

In the present work, we propose the synthesis of a new family of sugar derived 1,4:3,6-dianhydrohexitol based AA/AB-type monomers. Unprecedented diacids based on Isomannide and Isoidide were elaborated with high yields and showed interestingly high melting point ranges (240–375 °C). Optimization of reaction conditions (temperature, time of reaction, and reactant ratios) has been investigated to synthesize the key intermediate of a set of AB monomers with acid, ester, and acid chloride functionalities. Isosorbide based ether benzoic acid AB monomer was polymerized and characterized by NMR and DSC techniques. The results show a semicrystalline behavior of the obtained polymer thanks to the controlled stereoregular arrangement of the AB starting monomer.

Copolymerization Kinetics of Glycidol and Ethylene Oxide, Propylene Oxide, and 1,2-Butylene Oxide: From Hyperbranched to Multiarm Star Topology

Copolymerization of established epoxide monomers with glycidol (G) is a key reaction to prepare branched or hyperbranched polyethers. The kinetics of the multibranching anionic ring-opening copolymerization of glycidol (a cyclic latent AB2 monomer) with ethylene oxide (EO), propylene oxide (PO), and 1,2-butylene oxide (BO; cyclic latent AB monomers), respectively, in dimethyl sulfoxide was studied. Online 1H NMR spectroscopy was employed for in situ monitoring of the individual monomer consumption during the entire course of the statistical copolymerization. Varying the counterion, both the cesium alkoxide and potassium alkoxide initiated copolymerization were studied and compared. From the individual monomer consumption, reactivity ratios were calculated. The reactivity ratio of the alkylene oxides decreases from 0.44 to 0.11 with increasing alkyl chain length on going from EO to BO. Unexpectedly, glycidol was found to exhibit a higher reactivity ratio in each copolymerization, with reactivity ratios ranging from 2.34 (with EO) to 7.94 (copolymerization with BO). Different counterions had an impact on absolute reaction rates, however, relative monomer reactivities remained unchanged. The reactivity ratios determine both the molecular weight distribution and the topology as well as the degree of branching (DB) of the respective branched copolymers, implying a change from a hyperbranched random copolymer (glycidol/EO) to a multiarm star structure with increasing side chain length of the alkylene comonomer.

Chain-growth condensation polymerization of 5-aminoisophthalic acid triethylene glycol ester to afford well-defined, water-soluble, thermoresponsive hyperbranched polyamides

Based on a model amidation reaction of benzoic acid triethylene glycol (TEG) ester with lithium anilide, which proceeded as rapidly as that of the methyl ester and faster than that of the ethyl ester, we considered that a TEG ester AB2 monomer would have sufficient reactivity to undergo chain-growth condensation polymerization. Indeed, condensation polymerization of 5-(methylamino)isophthalic acid TEG ester proceeded in a chain-growth polymerization manner in the presence of 1,1,1,3,3,3-hexamethyldisilazide (LiHMDS) and an initiator at −40 °C to afford a well-defined hyperbranched polyamide (HBPA) bearing many hydrophilic TEG ester moieties. The Mn values of the HBPA increased in proportion to the feed ratio of monomer to the initiator, with retention of low polydispersity (Mn = 6120–42200, Mw/Mn = 1.10–1.20). The degree of branching (DB) remained in the range of 0.48–0.51, irrespective of the feed ratio. A 0.25 wt% aqueous solution of HBPAs with different Mn values showed thermoresponsive behavior with a lower critical solution temperature (LCST) in the range of 35–37 °C, which is close to human body temperature, as in the case of poly(N-isopropylacrylamide).

Preparation of epoxy‐ended hyperbranched polymers with precisely controllable degree of branching by thiol‐ene Michael addition

ABSTRACTEpoxy‐ended hyperbranched polymers (EHPs) have a wide range of applications due to their outstanding performances. Because their microstructures are not positively identified, it is very difficult to ascertain the reinforcing and toughening mechanisms of EHPs and their interface interaction with other matrixes. Controllable synthesis of EHPs with precise degree of branching (DB) remains to be a major challenge. Here, a method for preparing novel nitrogen‐phosphor skeleton epoxy‐ended hyperbranched polymers (NPEHP) with controllable DB by a thiol‐ene Michael addition between thiol‐ended hyperbranched polymers (NPHSH) and glycidyl methacrylate have been firstly reported. NPHSH is synthesized by an esterification between hydroxyl‐ended hyperbranched polymers (NPHOH) and 3‐mercaptopropionic acid. NPHOH is prepared by a thiol‐ene Michael addition between methacrylate group of a monomer and thiol group of linear monomer (AB) and/or branched monomer (AB2). The molar ratio between the AB and AB2 monomers controls the DB of the products. The 1H NMR spectra analysis of NPHOH shows that their experimentally determined DBs are very close to their theoretical values, indicating good controllability of their DBs. The narrow molecular weight distributions of NPHOH, NPHSH, and NPEHP suggest high efficiency of the thiol‐ene Michael addition. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 44277.

Synthesis of hyperbranched-linear poly(N-isopropylacrylamide) polymers with a poly(siloxysilane) hyperbranched macroinitiator, and their application to cell culture on glass substrates

The attachment of poly(N-isopropylacrylamide) (PNIPAM) onto glass slides by using a hyperbranched poly(siloxysilane) (HBPS) as a linker was investigated to develop a thermoresponsive glass surface for cell sheet engineering. A reversible addition–fragmentation chain transfer (RAFT) polymerization chain transfer agent (CTA) was introduced onto the termini of the HBPS via the polycondensation of an AB2 monomer and subsequent suitable end-group modification. Living radical polymerization of NIPAM from the CTA-termini of HBPS was achieved, yielding a copolymer of HBPS and PNIPAM (HBPS-g-PNIPAM). The glass slides were PNIPAM-coated by drop casting of HBPS-g-PNIPAM in tetrahydrofuran (THF), and immobilization was confirmed by X-ray photoelectron spectroscopy, atomic force microscopy and contact angle measurements. The resulting glass slide was applied to cell culture of mouse 3T3 fibroblasts, and attachment and proliferation were successfully achieved at 37 °C after 2 or 4 days. Reducing the temperature to 20 °C for 15 min permitted the detachment of the cell sheet. The glass slide was successfully reused for cell culture, thus confirming the strong attachment of the polymer onto the surface. This paper describes the synthesis of hyperbranched poly(siloxysilane) grafted poly(N-isopropylacrylamide) (HBPS-g-PNIPAM), and its application to thermoresponsive cell culture onto glass substrate. PNIPAM branches were growth from the termini of HBPS via reversible addition–fragmentation chain transfer (RAFT) polymerization. The obtained HBPS-g-PNIPAM was casted from a tetrahydrofuran (THF) solution onto glass slides to fabricate a thermoresponsive surface for cell culture. Mouse 3T3 fibroblast cells were seeded and cultured at 37 °C for 4 days and detachment was possible by cooling the temperature to 20 °C for 15 min.

Investigate the Glass Transition Temperature of Hyperbranched Copolymers with Segmented Monomer Sequence

Hyperbranched copolymers with segmented structures were synthesized using a chain-growth copper-catalyzed azide–alkyne cycloaddition (CuAAC) polymerization via sequential monomer addition in one pot. Three AB2-type monomers that contained one alkynyl group (A), two azido groups (B), and one dangling group, either benzyl or oligo(ethylene oxide) (EOx, x = 3 and 7.5), were used in these CuAAC reactions. Varying the addition sequences and feed ratios of the monomers produced a variety of hyperbranched copolymers with tunable compositions, molecular weights, segmented structures, and consequently glass transition temperature (Tg). It was found that the Tg of hyperbranched copolymers was little affected by the polymer molecular weights when Mn ≥ 5000. However, the values of Tg were significantly determined by the compositions of the terminal groups and the outermost segment of the hyperbranched copolymers. The last added AB2 monomer in the polymerization formed an outermost “shell” and shielded the contributio...

Synthesis of Dense and Chiral Dendritic Polyols Using Glyconanosynthon Scaffolds.

Most classical dendrimers are frequently built-up from identical repeating units of low valency (usually AB2 monomers). This strategy necessitates several generations to achieve a large number of surface functionalities. In addition, these typical monomers are achiral. We propose herein the use of sugar derivatives consisting of several and varied functionalities with their own individual intrinsic chirality as both scaffolds/core as well as repeating units. This approach allows the construction of chiral, dense dendrimers with a large number of surface groups at low dendrimer generations. Perpropargylated β-d-glucopyranoside, serving as an A5 core, together with various derivatives, such as 2-azidoethyl tetra-O-allyl-β-d-glucopyranoside, serving as an AB4 repeating moiety, were utilized to construct chiral dendrimers using “click chemistry” (CuAAC reaction). These were further modified by thiol-ene and thiol-yne click reactions with alcohols to provide dendritic polyols. Molecular dynamic simulation supported the assumption that the resulting polyols have a dense structure.

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...

Supramolecular polymerization induced self-assembly into micelle and vesicle via acid–base controlled formation of fluorescence responsive supramolecular hyperbranched polymers

Micellar and vesicular aggregates were achieved in situ by supramolecular polymerization of π-conjugated AB2 monomers with dibenzo-24-crown-8 and dibenzylammonium groups.

A minimalist furan–maleimide AB-type monomer and its thermally reversible Diels–Alder polymerization

An original approach to prepare and polymerize the shortest Diels–Alder AB monomer.

A Scalable and High-Yield Strategy for the Synthesis of Sequence-Defined Macromolecules.

The efficient synthesis of a sequence-defined decamer, its characterization, and its straightforward dimerization through self-metathesis are described. For this purpose, a monoprotected AB monomer was designed and used to synthesize a decamer bearing ten different and selectable side chains by iterative Passerini three-component reaction (P-3CR) and subsequent deprotection. The highly efficient procedure provided excellent yields and allows for the multigram-scale synthesis of such perfectly defined macromolecules. An olefin was introduced at the end of the synthesis, allowing the self-metathesis reaction of the resulting decamer to provide a sequence-defined 20-mer with a molecular weight of 7046.40 g mol(-1). The obtained oligomers were carefully characterized by NMR and IR spectroscopy, GPC and GPC coupled to ESI-MS, and mass spectrometry (FAB and orbitrap ESI-MS).

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).

A hyperbranched mechanically interlocked rotaxane-type polymer

The interaction of the diacid chloride (2) of N,N’-bis(5″-carboxypentyl)-4,4′bipyridnium bis(hexafluorophosphate) (1) with m-phenylene-5′-hydroxymethyl-1′,3′-phenylene-32-crown-10 (3) at −70 °C led to the in situ formation of a pseudorotaxane 4 as an AB2 monomer, which was allowed to polymerize by raising the temperature and adding a catalytic amount of pyridine. The resulting hyperbranched polymer was held together via mechanical bonds formed by threading of the crown ether units by the bipyridinium (paraquat) moieties. The polymer was initially precipitated into aqueous NH4PF6 to remove any unreacted, water soluble diacid 1 to form 5b and then precipitated from DMSO into aqueous NH4PF6 to remove any pyridinium monoester 8 complexed with crown ether units in the polymer, leading to 6. The hyprerbranched polyester was characterized by 1H NMR and NOESY spectroscopies, FAB and MALDI-TOF mass spectrometry and viscometry. NMR spectroscopy confirmed complete esterification of the crown ether alcohol; 5b contained 60% monoesterified paraquat units (8) and 40% diester moieties (9), while 6 contained only 24% monoester moieties, which existed primarily as “focal point” units (10), but also as uncomplexed linker units (11). A variety of mechanically linked structures containing cyclic units is possible, including 17–19. Mass spectrometry on 6 detected masses up to 16.3 kDa, corresponding to a degree of polymerization of 11 units of the diester repeat unit in 17 (and/or isomeric structures).

Synthesis and Characterization of Poly(Amideimide)S from Ab Monomers by Direct Polycondensation Using Triphenyl Phosphite

Poly(amideimide)s were prepared by the reaction of two new AB monomers, N-(4-aminophenyl)-4-(p-carboxyphenoxy)phthalimide and N-(3-aminophenyl)-4-(p-carboxyphenoxy)phthalimide. The monomers were synthesized by nucleophilic displacement reaction of the corresponding nitrophthalimides with p-hydroxybenzoic acid. The monomers were characterized by IR and NMR. Poly(amideimide)s were prepared from AB monomers by direct polycondensation using triphenyl phosphite. The polymers obtained had high inherent viscosities. The polymers showed high solubility in polar aprotic solvents. The polymers showed good thermal stability and had high glass transition temperatures. X-ray diffraction pattern of the polymers indicate amorphous nature of these polymers.

ChemInform Abstract: Low‐Polydispersity Hyperbranched Polyphenylene Sulfide as a Protectant for Palladium Nanocomposites.

AbstractA new hyperbranched poly(phenylene sulfide) (HPPS) is successfully synthesized by modified polycondensation of an AB2 monomer with a core molecule.

Synthesis of novel AB2 monomers for the construction of highly branched macromolecular architectures

A series of novel, structurally related AB 2 monomers was synthesized and incorporated into branched materials. Size exclusion chromatography was used to compare these systems based on their relative hydrodynamic volumes. The results of these studies indicated an increased hydrodynamic volume of bis-benzyl amine based AB 2 monomer relative to analogous bis-benzyl ether structures. In order to further explore the b is-benzyl amine AB 2 structural motif, additional monomers were synthesized, leading to new branched materials and hyperbranched polymer structures.