Synthesis of amphiphilic block copolymer consisting of glycopolymer and poly(l‐lactide) and preparation of sugar‐coated polymer aggregates

The block glycopolymer, poly(2‐(α‐d ‐mannopyranosyloxy)ethyl methacrylate)‐b‐poly(l ‐lactide) (PManEMA‐b‐PLLA), was synthesized via a coupling approach. PLLA having an ethynyl group was successfully synthesized via ring‐opening polymerization using 2‐propyn‐1‐ol as an initiator. The ethynyl functionality of the resulting polymer was confirmed by MALDI‐TOF mass spectroscopy. In contrast, PManEMA having an azide group was prepared via AGET ATRP using 2‐azidopropyl 2‐bromo‐2‐methylpropanoate as an initiator. The azide functionality of the resulting polymer was confirmed by IR spectroscopy. The Cu(I)‐catalyzed 1,3‐dipolar cycloaddition between PLLA and PManEMA was performed to afford PManEMA‐b‐PLLA. The block structure was confirmed by ¹H NMR spectroscopy and size exclusion chromatography. The aggregating properties of the block glycopolymer, PManEMA_16k‐b‐PLLA_6.4k (M _n,PManEMA = 16,000, M _n,PLLA = 6400) was examined by ¹H NMR spectroscopy, fluorometry using pyrene, and dynamic light scattering. The block glycopolymer formed complicated aggregates at concentrations above 21 mg·L^?1 in water. The d ‐mannose presenting property of the aggregates was also characterized by turbidimetric assay using concanavalin A. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55 , 395–403     

Simple route for synthesis of H‐shaped copolymers

The H‐shaped copolymers, [poly(L ‐lactide)]₂polystyrene [poly(L ‐lactide)]₂, [(PLLA)₂PSt(PLLA)₂] have been synthesized by combination of atom transfer radical polymerization (ATRP) with cationic ring‐opening polymerization (CROP). The first step of the synthesis is ATRP of St using α,α′‐dibromo‐p‐xylene/CuBr/2,2′‐bipyridine as initiating system, and then the PSt with two bromine groups at both chain ends (Br–PSt–Br) were transformed to four terminal hydroxyl groups via the reaction of Br–PSt–Br with diethanolamine in N,N‐dimethylformamide. The H‐shaped copolymers were produced by CROP of LLA, using PSt with four terminal hydroxyl groups as macroinitiator and Sn(Oct)₂ as catalyst. The copolymers obtained were characterized by ¹H NMR spectroscopy and gel permeation chromatography. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2794–2801, 2006     

Syntheses and micellar properties of well‐defined amphiphilic AB2 and A2B Y‐shaped miktoarm star copolymers of ε‐caprolactone and 2‐(dimethylamino)ethyl methacrylate

Well‐defined amphiphilic PCL‐b‐(PDMA)₂ and (PCL)₂‐b‐PDMA Y‐shaped miktoarm star copolymers and PCL‐b‐PDMA linear diblock copolymer were synthesized via a combination of ring‐opening polymerization (ROP) and atom transfer radical polymerization (ATRP), where PCL is poly (ε‐caprolactone) and PDMA is poly(2‐(dimethylamino)ethyl methacrylate). All of these three types of copolymers have comparable PCL contents and overall molecular weights. The PCL block is hydrophobic while the PDMA block is hydrophilic, and they behave like polymeric surfactants and self‐assemble into PCL‐core micelles in aqueous media. The chain architectural effects on the micellization properties, including the aggregation number, size, polydispersity, and micelle densities of (PCL₂₉)₂‐b‐PDMA₄₅, PCL₆₁‐b‐(PDMA₂₄)₂, and PCL₅₆‐b‐PDMA₄₉ in dilute aqueous solution, were then explored by dynamic and static laser light scattering (LLS). The intensity–average hydrodynamic radius, 〈R_h〉, the aggregation number per micelle, N_agg, and the core radius, R_core, of the PCL‐core micelles all increased in the order PCL₆₁‐b‐(PDMA₂₄)₂ < (PCL₂₉)₂‐b‐PDMA₄₅ < PCL₅₆‐b‐PDMA₄₉. The surface area occupied per soluble PDMA block at the core/corona interface increased in the order PCL₆₁‐b‐(PDMA₂₄)₂ < PCL₅₆‐b‐PDMA₄₉ < (PCL₂₉)₂‐b‐PDMA₄₅. PCL₆₁‐b‐(PDMA₂₄)₂ micelles had the largest overall micelle density, possibly because of that the presence of two soluble PDMA arms at the junction point favors the bending of the core–corona interface and thus the formation of densely‐packed core‐shell nanostructures. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1446–1462, 2007     

Preparation of comb‐like copolymers with amphiphilic poly(ethylene oxide)‐b‐polystyrene graft chains by combination of “graft from” and “graft onto” strategies

A novel method for preparation the comb‐like copolymers with amphihilic poly(ethylene oxide)‐block‐poly(styrene) (PEO‐b‐PS) graft chains by “graft from” and “graft onto” strategies were reported. The ring‐opening copolymerization of ethylene oxide (EO) and ethoxyethyl glycidyl ether (EEGE) was carried out first using α‐methoxyl‐ω‐hydroxyl‐poly(ethylene oxide) (mPEO) and diphenylmethyl potassium (DPMK) as coinitiation system, then the EEGE units on resulting linear copolymer mPEO‐b‐Poly(EO‐co‐EEGE) were hydrolyzed and the recovered hydroxyl groups were reacted with 2‐bromoisobutyryl bromide. The obtained macroinitiator mPEO‐b‐Poly(EO‐co‐BiBGE) can initiate the polymerization of styrene by ATRP via the “Graft from” strategy, and the comb‐like copolymers mPEO‐b‐[Poly(EO‐co‐Gly)‐g‐PS] were obtained. Afterwards, the TEMPO‐PEO was prepared by ring‐opening polymerization (ROP) of EO initiated by 4‐hydroxyl‐2,2,6,6‐tetramethyl piperdinyl‐oxy (HTEMPO) and DPMK, and then coupled with mPEO‐b‐[Poly(EO‐co‐Gly)‐g‐PS] by atom transfer nitroxide radical coupling reaction in the presence of cuprous bromide (CuBr)/N,N,N′,N″,N″‐pentamethyldiethylenetriamine (PMDETA) via “Graft onto” method. The comb‐like block copolymers mPEO‐b‐[Poly(EO‐co‐Gly)‐g‐(PS‐b‐PEO)] were obtained with high efficiency (≥90%). The final product and intermediates were characterized in detail. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 1930–1938, 2009     

Synthesis of amphiphilic A2B star‐shaped copolymers of polystyrene‐b‐[poly(ethylene oxide)]2 via atom transfer nitroxide radical coupling

The amphiphilic A₂B star‐shaped copolymers of polystyrene‐b‐[poly(ethylene oxide)]₂ (PS‐b‐PEO₂) were synthesized via the combination of atom transfer nitroxide radical coupling (ATNRC) with ring‐opening polymerization (ROP) and atom transfer radical polymerization (ATRP) mechanisms. First, a novel V‐shaped 2,2,6,6‐tetramethylpiperidine‐1‐oxyl‐PEO₂ (TEMPO‐PEO₂) with a TEMPO group at middle chain was obtained by ROP of ethylene oxdie monomers using 4‐(2,3‐dihydroxypropoxy)‐TEMPO and diphenylmethyl potassium as coinitiator. Then, the linear PS with a bromine end group (PS‐Br) was obtained by ATRP of styrene monomers using ethyl 2‐bromoisobutyrate as initiator. Finally, the copolymers of PS‐b‐PEO₂ were obtained by ATNRC between the TEMPO and bromide groups on TEMPO‐PEO₂ and PS‐Br, respectively. The structures of target copolymers and their precursors were all well‐defined by gel permeation chromatographic and nuclear magnetic resonance (¹H NMR). © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Synthesis of miktoarm star amphiphilic block copolymers via combination of NMRP and ATRP and investigation on self‐assembly behaviors

The novel trifunctional initiator, 1‐(4‐methyleneoxy‐2,2,6,6‐tetramethylpip‐eridinoxyl)‐3,5‐bi(bromomethyl)‐2,4,6‐trimethylbenzene (TEMPO‐2Br), was successfully synthesized and used to prepare the miktoarm star amphiphilic poly(styrene)‐(poly(N‐isopropylacrylamide))₂ (PS(PNIPAAM)₂) via combination of atom transfer radical polymerization (ATRP) and nitroxide‐mediated radical polymerization (NMRP) techniques. Furthermore, the star amphiphilic block copolymer, poly (styrene)‐(poly(N‐isopropylacrylamide‐b‐4‐vinylpyridine))₂ (PS(PNIPAAM‐b‐P4VP)₂), was also prepared using PS(PNIPAAM)₂ as the macroinitiator and 4‐vinylpyridine as the second monomer by ATRP method. The obtained polymers were well‐defined with narrow molecular weight distributions (M_w/M_n ≤ 1.29). Meanwhile, the self‐assembly behaviors of the miktoarm amphiphilic block copolymers, PS(PNIPAAM)₂ and PS(PNIPAAM‐b‐P4VP)₂, were also investigated. Interestingly, the aggregate morphology changed from sphere‐shaped micelles (4.7 < pH < 3.0) to a mixture of spheres and rods (1.0 < pH < 3.0), and rod‐shaped nanorods formed when pH value was below 1.0. The LCST of PS(PNIPAAM)₂ (pH = 7) was about 31 °C and the LCST of PS(PNIPAAM‐b‐P4VP)₂ was about 35 °C (pH = 3). © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 6304–6315, 2009     

Synthesis of diblock copolymers by combination of organocatalyzed ring‐opening polymerization and atom transfer radical polymerization using trichloroethanol as a bifunctional initiator

This study reports an application of trichloroethanol (TCE) as a bifunctional initiator for the synthesis of block copolymers (BCPs) by organocatalyzed ring‐opening polymerization (OROP) and atom transfer radical polymerization (ATRP). TCE was employed to synthesize a low dispersity poly (valerolactone) macroinitiator, which was subsequently used for the ATRP of tert‐butyl methacrylate. While it is known that TCE can serve as an initiator in ATRP, the ability to induce polymerization under OROP is reported for the first time. The formation of well‐defined BCPs was confirmed by gel permeation chromatography and ¹H NMR. Computational studies were performed to obtain a molecular‐level understanding of the ring‐opening polymerization mechanism involving TCE as initiator. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 563–569     

新型线状-树枝状两亲嵌段共聚物的合成

本文设计合成了一系列由不同链长的聚丙烯酸(PAA)为亲水嵌段和不同代数聚苄醚树枝体(Dendr.PBE)为疏水嵌段的杂化共聚物(PAA-Dendr.PBE)。     

Synthesis of poly(tetrahydrofuran)‐b‐polystyrene block copolymers from dual initiators for cationic ring‐opening polymerization and atom transfer radical polymerization

A dual initiator (4‐hydroxy‐butyl‐2‐bromoisobutyrate), that is, a molecule containing two functional groups capable of initiating two polymerizations occurring by different mechanisms, has been prepared. It has been used for the sequential two‐step synthesis of well‐defined block copolymers of polystyrene (PS) and poly(tetrahydrofuran) (PTHF) by atom transfer radical polymerization (ATRP) and cationic ring‐opening polymerization (CROP). This dual initiator contains a bromoisobutyrate group, which is an efficient initiator for the ATRP of styrene in combination with the Cu(0)/Cu(II)/N,N,N′,N″,N″‐pentamethyldiethylenetriamine catalyst system. In this way, PS with hydroxyl groups (PS‐OH) is formed. The in situ reaction of the hydroxyl groups originating from the dual initiator with trifluoromethane sulfonic anhydride gives a triflate ester initiating group for the CROP of tetrahydrofuran (THF), leading to PTHF with a tertiary bromide end group (PTHF‐Br). PS‐OH and PTHF‐Br homopolymers have been applied as macroinitiators for the CROP of THF and the ATRP of styrene, respectively. PS‐OH, used as a macroinitiator, results in a mixture of the block copolymer and remaining macroinitiator. With PTHF‐Br as a macroinitiator for the ATRP of styrene, well‐defined PTHF‐b‐PS block copolymers can be prepared. The efficiency of PS‐OH or PTHF‐Br as a macroinitiator has been investigated with matrix‐assisted laser desorption/ionization time‐of‐flight spectroscopy, gel permeation chromatography, and NMR. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3206–3217, 2003     

Organoboronium amphiphilic block copolymers

A new class of amphiphilic organometallic block copolymers with cationic organoboron pendant groups was developed. Selective replacement of one of the bromine substitutents on each boryl group of the block copolymer PSBBr₂‐b‐PS with an organometallic reagent ArM (ArM = 2,4,6‐trimethylphenyl copper, 4‐t‐butylphenyltrimethyl tin) followed by treatment with 2,2′‐bipyridine gave the novel block copolymers [ 3Ar ](Br)_n as light yellow solid materials that show good stability in air and moisture and high solubility in most organic solvents. Their structure and composition were confirmed by multinuclear NMR, GPC, and elemental analysis. Highly regular micellar aggregates form in block‐selective solvents (e.g., MeOH, toluene) as demonstrated by ¹H NMR, dynamic light scattering, and transmission electron microscopy. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 6612–6618, 2009     

Synthesis of amphiphilic A4B4 star‐shaped copolymers by mechanisms transformation combining with thiol‐ene reaction

Using core‐first strategy, the amphiphilic A₄B₄ star‐shaped copolymers [poly(ethylene oxide)]₄[poly(ε‐caprolactone)]₄ [(PEO)₄(PCL)₄], [poly(ethylene oxide)]₄[poly(styrene)]₄ [(PEO)₄(PS)₄], and [poly(ethylene oxide)]₄[poly(tert‐butyl acrylate)]₄ [(PEO)₄(PtBA)₄] were synthesized by mechanisms transformation combining with thiol‐ene reaction. First, using a designed multifunctional mikto‐initiator with four active hydroxyl groups and four allyl groups, the four‐armed star‐shaped polymers (PEO‐Ph)₄/(OH)₄ with four active hydroxyl groups at core position were obtained by sequential ring‐opening polymerization (ROP) of ethylene oxide monomers, capping reaction of living oxyanion with benzyl chloride, and transformation of allyl groups into hydroxyl groups by thiol‐ene reaction. Then, the A₄B₄ star‐shaped copolymers (PEO)₄(PS)₄ or (PEO)₄(PtBA)₄ were obtained by atom transfer radical polymerization (ATRP) of styrene or tert‐butyl acrylate (tBA) monomers from macroinitiator of (PEO‐Ph)₄/(Br)₄, which was obtained by esterification of (PEO‐Ph)₄/(OH)₄ with 2‐bromoisobutyryl bromide. The A₄B₄ star‐shaped copolymers (PEO)₄(PCL)₄ were also obtained by ROP of ε‐caprolactopne monomers from macroinitiator of (PEO‐Ph)₄/(OH)₄. The target copolymers and intermediates were characterized by size‐exclusion chromatography, matrix‐assisted laser desorption/ionization time‐of‐flight mass spectroscopy, and nuclear magnetic resonance in detail. This synthetic route might be a versatile one to various A_nB_n (n ≥ 3) star‐shaped copolymers with defined structure and compositions. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 4572–4583     

Atom transfer radical homo‐ and block copolymerization of methyl 1‐bicyclobutanecarboxylate

A non‐olefinic monomer, methyl 1‐bicyclobutanecarboxylate (MBC), was successfully polymerized by the controlled/“living” atom transfer radical polymerization (ATRP) technique, resulting in a well‐defined homopolymer, PMBC, with only cyclobutane ring units in the polymer chain. An AB block copolymer poly(methyl 1‐bicyclobutanecarboxylate)‐b‐polystyrene (PMBC‐b‐PS), having an all‐ring unit segment, was also synthesized with narrow polydispersity and designed number‐average molecular weight in addition to precise end groups. The ¹H NMR spectra, glass‐transition temperature, and thermal stability of PMBC, PMBC‐b‐PS, and PS‐b‐PMBC were investigated. The experimental results showed that the cyclobutane rings in the two block polymers improved their thermal stability. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1929–1936, 2002     

Synthesis and characterization of sulfonated block copolymers by atom transfer radical polymerization

Well‐defined sulfonated polystyrene and block copolymers with n‐butyl acrylate (nBA) were synthesized by CuBr catalyzed living radical polymerization. Neopentyl p‐styrene sulfonate (NSS) was polymerized with ethyl‐2‐bromopropionate initiator and CuBr catalyst with N,N,N′,N′‐pentamethylethyleneamine to give poly(NSS) (PNSS) with a narrow molecular weight distribution (MWD < 1.12). PNSS was then acidified by thermolysis resulting in a polystyrene backbone with 100% sulfonic acid groups. Random copolymers of NSS and styrene with various composition ratios were also synthesized by copolymerization of NSS and styrene with different feed ratios (MWD < 1.11). Well defined block copolymers with nBA were synthesized by sequential polymerization of NSS from a poly(n‐butyl acrylate) (PnBA) precursor using CuBr catalyzed living radical polymerization (MWD < 1.29). © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5991–5998, 2008     

Preparation of poly(ethylene oxide) star polymers and poly(ethylene oxide)–polystyrene heteroarm star polymers by atom transfer radical polymerization

Poly(ethylene oxide) (PEO) star polymer with a microgel core was prepared by atom transfer radical poylmerization (ATRP) of divinyl benzene (DVB) with mono‐2‐bromoisobutyryl PEO ester as a macroinitiator. Several factors, such as the feed ratio of DVB to the initiator, type of catalysts, and purity of DVB, play important roles during star formation. The crosslinked poly(divinyl benzene) (PDVB) core was further obtained by the hydrolysis of PEO star to remove PEO arms. Size exclusion chromatography (SEC) traces revealed the bare core has a broad molecular weight distribution. PEO–polystyrene (PS) heteroarm star polymer was synthesized through grafting PS from the core of PEO star by another ATRP of styrene (St) because of the presence of initiating groups in the core inherited from PEO star. Characterizations by SEC, ¹H NMR, and DSC revealed the successful preparation of the target star copolymers. Scanning electron microscopy images suggested that PEO–PS heteroarm star can form spherical micelles in water/tetrahydrofuran mixture solvents, which further demonstrated the amphiphilic nature of the star polymer. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2263–2271, 2004     

Ambient temperature ATRP of benzyl methacrylate as a tool for the synthesis of block copolymers with styrene

The rapid atom transfer radical polymerization (ATRP) of benzyl methacrylate (BnMA) at ambient temperature was used to synthesize block copolymers with styrene as the second monomer. Various block copolymers such as AB diblock, BAB symmetric and asymmetric triblock, and ABABA pentablock copolymers were synthesized in which the polymerization of one of the blocks namely BnMA was performed at ambient temperature. It is demonstrated that the block copolymerization can be performed in a controlled manner, regardless of the sequence of monomer addition via halogen exchange technique. Using this reaction condition, the composition (ratio) of one block (here BnMA) can be varied from 1 to 100. It is further demonstrated that in the multiblock copolymer syntheses involving styrene and benzyl methacrylate, it is better to start from the PS macroinitiator compared with PBnMA macroinitiator. The polymers synthesized are relatively narrow dispersed (<1.5). It is identified that the ATRP of BnMA is limited to certain molecular weights of the PS macroinitiator. Additionally, a preliminary report about the synthesis of the block copolymer of BnMA‐methyl methacrylate (MMA), both at ambient temperature, is demonstrated. Subsequent deprotection of the benzyl group using Pd/C? H₂ results in methacrylic acid (MAA)–methyl methacrylate (MAA–MMA) amphiphilic block copolymer. GPC, IR, and NMR are used to characterize the synthesized polymers. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2848–2861, 2006     

Synthesis and characterization of amphiphilic triblock copolymers by iron‐mediated atom transfer radical polymerization

The atom transfer radical polymerization of methyl methacrylate (MMA) and n‐butyl methacrylate (n‐BMA) was initiated by a poly(ethylene oxide) chloro telechelic macroinitiator synthesized by esterification of poly(ethylene oxide) (PEO) with 2‐chloro propionyl chloride. The polymerization, carried out in bulk at 90 °C and catalyzed by iron(II) chloride tetrahydrate in the presence of triphenylphosphine ligand (FeCl₂ · 4H₂O/PPh₃), led to A–B–A amphiphilic triblock copolymers with MMA or n‐BMA as the A block and PEO as the B block. A kinetic study showed that the polymerization was first‐order with respect to the monomer concentration. Moreover, the experimental molecular weights of the block copolymers increased linearly with the monomer conversion, and the molecular weight distribution was acceptably narrow at the end of the reaction. These block copolymers turned out to be water‐soluble through the adjustment of the content of PEO blocks (PEO content >90% by mass). When the PEO content was small [monomer/macroinitiator molar ratio (M/I) = 300], the block copolymers were water‐insoluble and showed only one glass‐transition temperature. With an increase in the concentration of PEO (M/I = 100 or 50) in the copolymer, two glass transitions were detected, indicating phase separation. The macroinitiator and the corresponding triblock copolymers were characterized with Fourier transform infrared, proton nuclear magnetic resonance, size exclusion chromatography analysis, dynamic mechanical analysis, and differential scanning calorimetry. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 5049–5061, 2005     

Preparation of polyethylene block copolymers by a combination of postmetallocene catalysis of ethylene polymerization and atom transfer radical polymerization

The synthesis of block copolymers consisting of a polyethylene segment and either a poly(meth)acrylate or polystyrene segment was accomplished through the combination of postmetallocene-mediated ethylene polymerization and subsequent atom transfer radical polymerization. A vinyl-terminated polyethylene (number-average molecular weight = 1800, weight-average molecular weight/number-average molecular weight =1.70) was synthesized by the polymerization of ethylene with a phenoxyimine zirconium complex as a catalyst activated with methylalumoxane (MAO). This polyethylene was efficiently converted into an atom transfer radical polymerization macroinitiator by the addition of α-bromoisobutyric acid to the vinyl chain end, and the polyethylene macroinitiator was used for the atom transfer radical polymerization of n-butyl acrylate, methyl methacrylate, or styrene; this resulted in defined polyethylene-b-poly(n-butyl acrylate), polyethylene-b-poly(methyl methacrylate), and polyethylene-b-polystyrene block copolymers. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 496–504, 2004     

Synthesis and characterization of amphiphilic heterograft copolymers with PAA and PS side chains via “Grafting from” approach

The amphiphilic heterograft copolymers poly(methyl methacrylate‐co‐2‐(2‐bromoisobutyryloxy)ethyl methacrylate)‐graft‐(poly(acrylic acid)/polystyrene) (P(MMA‐co‐BIEM)‐g‐(PAA/PS)) were synthesized successfully by the combination of single electron transfer‐living radical polymerization (SET‐LRP), single electron transfer‐nitroxide radical coupling (SET‐NRC), atom transfer radical polymerization (ATRP), and nitroxide‐mediated polymerization (NMP) via the “grafting from” approach. First, the linear polymer backbones poly(methyl methacrylate‐co‐2‐(2‐bromoisobutyryloxy)ethyl methacrylate) (P(MMA‐co‐BIEM)) were prepared by ATRP of methyl methacrylate (MMA) and 2‐hydroxyethyl methacrylate (HEMA) and subsequent esterification of the hydroxyl groups of the HEMA units with 2‐bromoisobutyryl bromide. Then the graft copolymers poly(methyl methacrylate‐co‐2‐(2‐bromoisobutyryloxy)ethyl methacrylate)‐graft‐poly(t‐butyl acrylate) (P(MMA‐co‐BIEM)‐g‐PtBA) were prepared by SET‐LRP of t‐butyl acrylate (tBA) at room temperature in the presence of 2,2,6,6‐tetramethylpiperidin‐1‐yloxyl (TEMPO), where the capping efficiency of TEMPO was so high that nearly every TEMPO trapped one polymer radicals formed by SET. Finally, the formed alkoxyamines via SET‐NRC in the main chain were used to initiate NMP of styrene and following selectively cleavage of t‐butyl esters of the PtBA side chains afforded the amphiphilic heterograft copolymers poly(methyl methacrylate‐co‐2‐(2‐bromoisobutyryloxy)ethyl methacrylate)‐graft‐(poly(t‐butyl acrylate)/polystyrene) (P(MMA‐co–BIEM)‐g‐(PtBA/PS)). The self‐assembly behaviors of the amphiphilic heterograft copolymers P(MMA‐co–BIEM)‐g‐(PAA/PS) in aqueous solution were investigated by AFM and DLS, and the results demonstrated that the morphologies of the formed micelles were dependent on the grafting density. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Preparation of reactive block copolymers and their transformation to hollowed nanostructures

A novel polymeric hollow nanostructure was generated using micellar template method through a three‐step procedure. First, the block copolymers were synthesized via ring‐opening metathesis polymerization by sequentially adding monomers 7‐oxanorborn‐5‐ene‐exo‐exo‐2,3‐dicarboxylic acid dimethyl ester and the mixture of norbornene and 2,3‐bis(2‐bromoisobutyryloxymethyl)‐5‐norbornene in chloroform, and also atom transfer radical polymerization of 4‐(3‐butenyl)styrene was carried out by using the as‐obtained block copolymer poly(7‐oxanorborn‐5‐ene‐exo,exo‐2,3‐dicarboxylic acid dimethylester)‐block‐poly(norbornene‐co‐2,3‐bis(2‐bromoisobutyryloxymethyl)‐5‐norbornene as macroinitiator to afford a graft copolymer bearing poly(4‐(3‐butenyl)styrene) branch poly(7‐oxanorborn‐5‐ene‐exo,exo‐2,3‐dicarboxylic acid dimethylester)‐block‐poly(norbornene‐co‐2,3‐bis(2‐bromoisobutyryloxymethyl)‐5‐norbornene)‐graft‐poly(4‐(3‐butenyl)styrene). Second, the shell‐crosslinked micelles were prepared by ruthenium‐mediated ring‐closing metathesis of poly(4‐(3‐butenyl)styrene) branches in intramicelle formed from the copolymers self‐assembly spontaneously in toluene. Finally, the hollowed spherical nanoparticles were presented by removing the micellar copolymer backbone through the cleavage of the ester bonds away from the crosslinked network of branches. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011