Hyperbranched Macroinitiator Research Articles

Synthesis of Unimolecular Micelles with Incorporated Hyperbranched Boltorn H30 Polyester modified with Hyperbranched Helical Poly(phenyl isocyanide) Chains and their Enantioselective Crystallization Performance.

Here, the fabrication of unimolecular micelles functionalized with helical polymeric chains as a chiral nucleating agent in enantioselective crystallization is reported. Starting from a fractionated hyperbranched polyester (Boltorn H30), the ring-opening polymerization of l-lactic acid (LLA) and subsequent terminal-group modification affords the alkyne-Pd(II)-anchored hyperbranched macroinitiator (H30-PLLA-Pd). By taking advantage of a Pd(II)-catalyzed living polymerization of chiral pendant modified l- or d-phenyl isocyanide (PI) monomers, well-defined chiral unimolecular micelles (H30-PLLA-PPI) grafted with radiating helical PPI coronas of one predominant screw sense are obtained. The resultant chiral materials demonstrate excellent application in the enantioselective crystallization of racemic threonine in water, and a 92% enantiomeric excess value of the residual solution is obtained. It is believed this present proof of concept and methodology are facile and powerful for preparing novel and versatile chiral materials with different topological structures, not only applicable to PPI but also to other types of polymers.

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.

Kinetic Model of the Amphiphilic Copolymers with Hyperbranched Core Formed by AB2Monomer and BfInitiator

The kinetic model of the amphiphilic copolymers with hyperbranched core and linear arms was developed for both semibatch and one-pot polymerization. The molecular size distribution functions of the species obtained and the various molecular parameters were analytically derived. The topological structures and molecular parameters of the products depend on initial mole feed ratios of the reactants. Under the same reaction conditions, the polydispersity index of the products resulted from semibatch is smaller than that of the one-pot process and there are more terminal units on the surface of hyperbranched macroinitiators from semibatch process. Accordingly, the topological structures of the amphiphilic hyperbranched copolymers and the successive self-assembly shapes can be designed by the suitable initial conditions of the polymerization.

制御されたハイパーブランチポリアミドマクロ開始剤によるリニア–ハイパーブランチブロック共重合体の合成

本報ではAB2モノマーの連鎖縮合重合によって合成した分子量と分子量分布の制御されたハイパーブランチポリアミド(HBPA)をマクロ開始剤とし，種々のリビング重合を行うことでリニア–ハイパーブランチジブロック共重合体を制御して合成したので報告する．まず，HBPAマクロ開始剤からメタクリル酸メチル(MMA)の原子移動ラジカル重合(ATRP)を行い，ポリメタクリル酸メチル(PMMA)とHBPAとのジブロック共重合体が分子量と分子量分布を制御して得られることを明らかにした．さらに，HBPAマクロ連鎖移動剤やヒドロキシ基をフォーカルポイントに有するHBPAマクロ開始剤を用いて，スチレンの可逆付加開裂連鎖移動(RAFT)重合やε-カプロラクトンの開環重合(ROP)を行い，分子量分布の狭いリニア–ハイパーブランチブロック共重合体をそれぞれ合成した．

Toward unimolecular micelles with tunable dimensions using hyperbranched dendritic-linear polymers.

A library of amphiphilic, hyperbranched dendritic-linear polymers (HBDLPs) are successfully synthesized, and evaluated as potential unimolecular micelles. Hyperbranched macroinitiators (HBMI), extended with poly(ethylene glycol) methacrylate (P(OEGMA)), are afforded via a combination of self-condensing vinyl (co)polymerization (SCV(C)P) and atom transfer radical polymerization (ATRP), providing a versatile two-step synthetic route. The HBDLP architecture and chain lengths are varied, and the effect on the nanoparticle (NP) stability and properties are evaluated. The HBDLPs form predominantly stable and spherical NPs, and the NP dimensions could be tailored by the HBDLP characteristics. The NPs formed are of high molecular weight, and their stability varies with the properties of the corresponding HBDLP. Too small dendritic segment, or too low degree of PEGylation, results to some extent in NP aggregation, while higher molecular weight HBDLPs, with a high amount of hydrophilic segments, appears to form discrete unimolecular micelles. The versatility of the platform is further demonstrated by the convenience of forming a HBDLP with a more complex, linear copolymer extension instead of P(OEGMA).

Polymerization: Assembly of Free‐Standing Polypeptide Films via the Synergistic Combination of Hyperbranched Macroinitiators, the Grafting‐From Approach, and Cross‐Chain Termination (Adv. Mater. 33/2013)

Polymerization: Assembly of Free‐Standing Polypeptide Films via the Synergistic Combination of Hyperbranched Macroinitiators, the Grafting‐From Approach, and Cross‐Chain Termination (Adv. Mater. 33/2013)

Assembly of Free‐Standing Polypeptide Films via the Synergistic Combination of Hyperbranched Macroinitiators, the Grafting‐From Approach, and Cross‐Chain Termination

Cross-linked polypeptide-based films are fabricated via a novel and robust method employing surface-initiated ring opening polymerization of α-amino acid N-carboxyanhydrides (NCA-ROP). The judicious combination of amine-based hyperbranched macroinitiators and benzyl ester-protected NCA derivatives promotes network formation by cross-chain terminations, which allows the formation of stable cross-linked peptide-based capsules in a one-pot system.

Systhesis of double-hydrophilic core-shell type multiarm star copolymer polyethylenimine-block-poly(2-hydroxyethyl methacrylate

Multiarm star block copolymers hyperbranched polyethylenimine-b-poly(2-hydroxyethyl methacrylate) (HPEI-b-PHEMA) with average 28 PHEMA arms have been prepared by atom transfer radical polymerization (ATRP) of HEMA in a mixed solvent of methanol and water using a core-first strategy. The hyperbranched macroinitiator employed was prepared on the basis of well-defined hyperbranched polyethylenimine with Mw/Mn of 1.04 by amidation with 2-bromo-isobutyryl bromide. The polymerization condition was optimized to prepare star copolymers with narrow dispersity, and the variables included the volume ratio of methanol to water, the molar ratio of initiating site to CuCl and the molar ratio of [CuCl]:[CuBr2]. Under the optimized polymerization condition, the lowest Mw/Mn value of the obtained star copolymers was around 1.3. Kinetic analysis showed that an induction period existed in the polymerization of HEMA. After this induction period, a linear dependence of ln([M]0/[M]t) on time was observed. The obtained HPEI-b-PHEMA could adsorb hydrophilic molecules. The comparison with the star copolymer with hydrophobic core and hydrophilic PHEMA shell verified that both the hydrophilic core and shell could host the hydrophilic guests, but the amidated HPEI core was more effective than the PHEMA shell.

Multiarm star poly(glycidol)- block-poly(styrene) as modifier of anionically cured diglycidylether of bisphenol A thermosetting coatings

Well-defined multiarm star copolymer poly(glycidol)- b-poly(styrene) (PGOH- b-PS) with an average number of PS arms per molecule of 85 has been prepared. The core first approach has been selected as the methodology using atom transfer radical polymerization (ATRP) of styrene to grow the arms from an activated hyperbranched poly(glycidol) as core. This activated hyperbranched macroinitiator was prepared by esterification of hyperbranched poly(glycidol) (PGOH) with 2-bromoisobutyryl bromide. PGOH- b-PS was used to modify diglycidylether of bisphenol A coatings cured by anionic ring-opening mechanism using 1-methyl imidazole as the initiator. The kinetics of the curing process, studied by dynamic scanning calorimetry (DSC), was not much affected when PGOH- b-PS was added to the formulation. By rheometry the effect of this new polymer topology on the complex viscosity ( η *) of the reactive mixture was analyzed. The phase-separation of the modified coatings was proved by dynamic thermomechanical analysis (DMTA) and electronic microscopy (SEM and TEM) showing nano- or microphase separation as a function of the modifier content. The addition of this star polymer led to increase in the rigidity in terms of Young's modulus and in the microhardness in comparison to neat DGEBA.

Synthesis, characterization, and rheological properties of multiarm stars with poly(glycidol) core and poly(methyl methacrylate) arms by AGET ATRP

Well-defined multiarm star block copolymers poly(glycidol)-b-poly(methyl methacrylate) (PGOHBr-b-PMMAx) with an average number of PMMA arms of 85, 55, and 45 have been prepared. The core-first approach has been selected as the methodology using atom transfer radical polymerization (ATRP) of MMA from an activated hyperbranched poly(glycidol) as the core. These activated hyperbranched macroinitiators were prepared by esterification of hyperbranched poly(glycidol) (PGOH) with 2-bromoisobutyryl bromide. The effect of monomer/initiator ratio, catalyst concentration, time, temperature, and solvent on the growing of the arms has been studied in detail in order to optimize the process and to diminish the radical-radical coupling. The final products and intermediates were characterized by means of size exclusion chromatography (SEC), nuclear magnetic resonance (NMR) and Fourier transform-infrared (FTIR) spectroscopy. The length of PMMA arms was determined by SEC after cleavage of ester bond linked to PGOH core. Glass transition temperature (Tg), thermal stability and rheological properties of the multiarm star copolymers were also studied. Finally, tapping mode atomic force microscopy (TMAFM) allowed the clear visualization of nano-sized particles (80–200 nm) corresponding to individual star molecules. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011

Focus on polymer chemistry papers in Science China Chemistry of the year 2010

In their researches, two kinds of novel temperature-responsive hyperbranched multiarm copolymers were successfully synthesized via the atom transfer radical polymerization (ATRP). Poly(3-ethyl-3-(hydroxymethyl) oxetane) (HBPO) core and thermosensitive poly(N-isopropylacrylamide) (PNIPAM) arms were synthesized from NIPAM monomers by using a hyperbranched HBPO macroinitiator. Moreover, poly(L-lactide) (PLA) inner-shell and poly(ethylene glycol) (PEG) outer-shell with disulfide-linkages between the hydrophobic and hydrophilic moieties was developed as unimolecular micelles. The HBPO-star-PNIPAM self-assembled micelles showed much improved drug encapsulation efficiencies and temperature-dependent sustainable release behavior due to the special micellar structure. The micelles exhibited no apparent cytotoxicity against human HeLa

Preparation of Well-Defined Star Polymer from Hyperbranched Macroinitiator Based Attapulgite by Surface-Initiated Atom Transfer Radical Polymerization Technique

To prepare the well-defined star polymer grafted attapulgite nanofibrillar clay (WSP-ATP) with hydrophilic core and hydrophobic shell and higher percentage of grafting, the postgraft polymerization of vinyl polymer from hyperbranched macroinitiator based attapulgite (HMI-ATP) via the surface-initiated atom transfer radical polymerization (SI-ATRP) technique was investigated for the first time. The HMI-ATP, with bromoacetic ester surface groups, was prepared by the bromoacetylation of the surface hydroxyl groups of the hyperbranched aliphatic polyester grafted attapulgite (HAPE-ATP). The HAPE-ATP was prepared by the one-pot polycondensation of the AB2-type monomer 2,2-bis(hydroxymethyl)propionic acid (bis-MPA), from the surfaces of the amino group modified attapulgite nanofibrillar clay (A-ATP) with p-toluenesulfonic acid (p-TSA) as catalyst. Then the SI-ATRP of methyl methacrylate (MMA) was conducted from the HMI-ATP made in the presence of 1,10-phenanthroline and Cu(I)Br as catalyst in toluene. The postg...

Synthesis of hyperbranched copolymers by combining enzymatic ring-opening polymerization and ATRP from a novel bifunctional initiator

The hyperbranched aliphatic polyester P(e-CL) was synthesized by means of Novozyme435-catalyzed ring-opening polymerization (ROP) of BHB (2, 2-bis(hydroxymethyl) butyric acid). The chains ended with hydroxyl of P(e-CL) were modified by the esterification of α-bromopropionyl bromide to obtain hyperbranched difunctional macroinitiator, which was used in the ATRP of St. CuCl/HMTETA was used as the catalyst system in the reaction of ATRP to acquire the hyperbranched copolymers polystyrene-blockpoly(2,2-bis(hydroxymethyl) butyric acid). The copolymer was confirmed by NMR and GPC.

Two‐dimensional regular nanopatterning on block copolymer substrate having lamellar morphology using star‐hyperbranched nanospheres by electrostatic interaction

AbstractHyperbranched polystyrenes (PS) were prepared by living radical photopolymerization of 4‐vinylbenzyl N,N‐diethyldithiocarbamate as an inimer under UV irradiation. The star‐hyperbranched copolymers were derived by grafting from surface N,N‐diethyldithiocarbamate groups of hyperbranched macroinitiator with t‐butyl methacrylate in the presence of N,N‐tetraethylthiuram disulfide. We obtained poly(methacrylic acid) star‐hyperbranched PS nanospheres by hydrolysis of poly(t‐butyl methacrylate)‐grafted chains. We established two‐dimensional (2D) regular nanopatterning by aligning continuously such nanospheres on poly(2‐vinylpyridine) (P2VP) lamellar layers of PS‐block‐P2VP diblock copolymer film. Electrostatic interaction between nanosphere surface having negative charges (COOCs) and P2VP lamellar layer acted effectively for the 2D nanopattern formation. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 4206–4210, 2006

Synthesis of Multiarm Star Poly(glycerol)-block-Poly(2-hydroxyethyl methacrylate)

Well-defined multiarm star block copolymers poly(glycerol)-b-poly(2-hydroxyethyl methacrylate) (PG-b-PHEMA) with an average of 56, 66, and 90 PHEMA arms, respectively, have been prepared by atom transfer radical polymerization (ATRP) of HEMA in methanol by a core-first strategy. The hyperbranched macroinitiators employed were prepared on the basis of well-defined hyperbranched polyglycerol by esterification with 2-bromoisobutyryl bromide. Polydispersites M(w)/M(n) of the new multiarm stars were in the range of 1.11-1.82. Unexpectedly, with the combination of CuCl/CuBr(2)/2,2'-bipyridyl as catalyst, the polymerization conversion can be driven to maximum values of 79%. The control of CuCl catalyst concentration is also very important to achieve high conversion and narrow polydispersity. The absolute M(n) values of the obtained multiarm star polymers were in good agreement with the calculated ones, and the highest M(n) values of the multiarm star copolymer is around 10(6) g/mol. Kinetic analysis shows that an induction period exists in the polymerization of HEMA. After this induction period, a linear dependence of ln ([M](0)/[M](t)()) on time was observed. Due to the star architecture, the viscosity of the obtained multiarm star PHEMA is much lower than that of linear PHEMA.

Multi‐Arm Star Polyglycerol‐block‐poly(tert‐butyl acrylate) and the Respective Multi‐Arm Poly(acrylic acid) Stars

AbstractSummary: Well‐defined multi‐arm star block copolymers, polyglycerol‐block‐poly(tert‐butyl acrylate) (PG‐b‐PtBA), with average arm‐numbers of 17, 27, 36, 66 and 90 arms, respectively, have been prepared by atom transfer radical polymerization (ATRP) of tBA in acetone, using a core‐first strategy. After hydrolysis with excess concentrated HCl in refluxing dioxane, full hydrolysis of the tert‐butyl ester groups was achieved, resulting in multi‐arm star polyelectrolytes, polyglycerol‐block‐poly(acrylic acid) (PG‐b‐PAA). The hyperbranched macroinitiators employed were prepared on the basis of hyperbranched polyglycerols via esterification with 2‐bromoisobutyryl bromide. Both CuBr/PMDETA and CuBr/Me6TREN catalyst systems have been employed for ATRP of tBA. CuBr/PMDETA was found to permit good control. Polydispersity indices for the new multi‐arm stars were mainly in the range of 1.22 to 1.4, and the absolute $\overline M _{\rm n}$ data were in agreement with the calculated values. Moreover, kinetic curves show a linear dependence of ln([M]0/[M]t) on time, confirming that the polymerizations are controlled.Relationship between arm numbers of the multi‐arm stars and maximum conversion achieved.imageRelationship between arm numbers of the multi‐arm stars and maximum conversion achieved.

Nanopattern formation on polymer substrate using star-hyperbranched nanospheres

Hyperbranched polystyrenes (PS) were prepared by living radical photopolymerization of 4-vinylbenzyl N, N-diethyldithiocarbamate as an inimer under UV irradiation. These hyperbranched PS exhibited large amounts of photofunctional dithiocarbamate groups on their outside surfaces. Subsequently, we derived the star-hyperbranched copolymers by grafting from hyperbranched macroinitiator with t-butyl methacrylate. We obtained poly(methacrylic acid) star-hyperbranched PS nanospheres by hydrolysis of poly( t-butyl methacrylate) grafted chains. We studied in detail two-dimensional nanopattern formation on poly(4-vinylpyridine) (P4VP) or partially quaternized P4VP substrate using such nanospheres by electrostatic interaction.

Solution properties of hyperbranched polymers and synthetic application for amphiphilic star‐hyperbranched copolymers by grafting from hyperbranched macroinitiator

AbstractHyperbranched polystyrenes (PS) were prepared by living radical photopolymerization of N,N‐diethyldithiocarbamoylmethylstyrene (DTCS) as an inimer under UV irradiation. Branched PS with an average chain length between branching points of four styrene units was also prepared by living radical copolymerization of DTCS with styrene. The ratio of radius of gyration to hydrodynamic radius RG/RH for these hyperbranched polymers was in the range 0.82–0.89 in toluene. The translational diffusion coefficient D(C) showed a constant value in the range of 0–14 × 10−3 g ml−1 in toluene. It was found from these dilute solution properties that hyperbranched PSs formed a unimolecular structure even in a good solvent because of their compact nature. These hyperbranched PSs exhibited large amounts of photofunctional carbamate (DC) groups on their outside surfaces. Subsequently, we derived amphiphilic star‐hyperbranched copolymers by grafting from hyperbranched macroinitiator with 1‐vinyl‐2‐pyrrolidinone. These star‐hyperbranched copolymers were soluble in water and methanol.© 2001 Society of Chemical Industry

Synthesis of new amphiphilic star polymers derived from a hyperbranched macroinitiator by the cationic ‘grafting from’ method

New amphiphilic star polymers possessing a hyperbranched core and hydrophilic graft arms have been prepared. The synthetic strategy involved esterification of the 4,4-bis(4′-hydroxyphenyl)valeric acid based hyperbranched polymer with 3-(chloromethyl)benzoyl chloride to obtain the hyperbranched macroinitiator followed by cationic ring-opening polymerization of 2-methyl-2-oxazoline to give amphiphilic polymers. Exchange of the chloride counter ion with trifluoromethanesulfonate (KCF3SO3 or AgCF3SO3) or iodide (KI) anions leads to higher polymerization rates. Phenyl 2-(chloromethyl)benzoate was used as a model initiator to study the effect of different coinitiators on the initiator efficiency. KI as a coinitiator yielded 56–86% initiator conversion whereas only 30–37% initiator conversion was achieved with KCF3SO3 or AgCF3SO3 as coinitiator after quantitative monomer consumption. Photon correlation spectroscopy (PCS) in methanol and chloroform for selected graft copolymers revealed the formation of single star molecules ranging from 22 to 50 nm in diameter.

Synthesis of new amphiphilic star polymers derived from a hyperbranched macroinitiator by the cationic ‘grafting from’ method

New amphiphilic star polymers possessing a hyperbranched core and hydrophilic graft arms have been prepared. The synthetic strategy involved esterification of the 4,4-bis(4′-hydroxyphenyl)valeric acid based hyperbranched polymer with 3-(chloromethyl)benzoyl chloride to obtain the hyperbranched macroinitiator followed by cationic ring-opening polymerization of 2-methyl-2-oxazoline to give amphiphilic polymers. Exchange of the chloride counter ion with trifluoromethanesulfonate (KCF3SO3 or AgCF3SO3) or iodide (KI) anions leads to higher polymerization rates. Phenyl 2-(chloromethyl)benzoate was used as a model initiator to study the effect of different coinitiators on the initiator efficiency. KI as a coinitiator yielded 56–86% initiator conversion whereas only 30–37% initiator conversion was achieved with KCF3SO3 or AgCF3SO3 as coinitiator after quantitative monomer consumption. Photon correlation spectroscopy (PCS) in methanol and chloroform for selected graft copolymers revealed the formation of single star molecules ranging from 22 to 50 nm in diameter.