Synthesis of miktoarm star and miktoarm star block copolymers via a combination of atom transfer radical polymerization and stable free‐radical polymerization

A trifunctional initiator, 2‐phenyl‐2‐[(2,2,6,6‐tetramethyl)‐1‐piperidinyloxy] ethyl 2,2‐bis[methyl(2‐bromopropionato)] propionate, was synthesized and used for the synthesis of miktoarm star AB₂ and miktoarm star block AB₂C₂ copolymers via a combination of stable free‐radical polymerization (SFRP) and atom transfer radical polymerization (ATRP) in a two‐step or three‐step reaction sequence, respectively. In the first step, a polystyrene (PSt) macroinitiator with dual ω‐bromo functionality was obtained by SFRP of styrene (St) in bulk at 125 °C. Next, this PSt precursor was used as a macroinitiator for ATRP of tert‐butyl acrylate (tBA) in the presence of Cu(I)Br and pentamethyldiethylenetriamine at 80 °C, affording miktoarm star (PSt)(PtBA)₂ [where PtBA is poly(tert‐butyl acrylate)]. In the third step, the obtained St(tBA)₂ macroinitiator with two terminal bromine groups was further polymerized with methyl methacrylate by ATRP, and this resulted in (PSt)(PtBA)₂(PMMA)₂‐type miktoarm star block copolymer [where PMMA is poly(methyl methacrylate)] with a controlled molecular weight and a moderate polydispersity (weight‐average molecular weight/number‐average molecular weight < 1.38). All polymers were characterized by gel permeation chromatography and ¹H NMR. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2542–2548, 2003     

ROMP‐NMP‐ATRP combination for the preparation of 3‐miktoarm star terpolymer via click chemistry

A combination of ring opening metathesis polymerization (ROMP) and click chemistry approach is first time utilized in the preparation of 3‐miktoarm star terpolymer. The bromide end‐functionality of monotelechelic poly(N‐butyl oxanorbornene imide) (PNBONI‐Br) is first transformed to azide and then reacted with polystyrene‐b‐poly(methyl methacrylate) copolymer with alkyne at the junction point (PS‐b‐PMMA‐alkyne) via click chemistry strategy, producing PS‐PMMA‐PNBONI 3‐miktoarm star terpolymer. PNBONI‐Br was prepared by ROMP of N‐butyl oxanorbornene imide (NBONI) 1 in the presence of (Z)‐but‐2‐ene‐1,4‐diyl bis(2‐bromopropanoate) 2 as terminating agent. PS‐b‐PMMA‐alkyne copolymer was prepared successively via nitroxide‐mediated radical polymerization (NMP) of St and atom transfer radical polymerization (ATRP) of MMA. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 497–504, 2009     

Synthesis of ABCD 4‐miktoarm star polymers by combination of RAFT,ROP, and “Click Chemistry”

The ABCD 4‐miktoarm star polymers based on polystyrene (PS), poly(ε‐caprolactone) (PCL), poly(methyl acrylate) (PMA), and poly(ethylene oxide) (PEO) were synthesized and characterized successfully. Using the mechanism transformation strategy, PS with three different functional groups (i.e., hydroxyl, alkyne, and trithiocarbonate), PS‐HEPPA‐SC(S)SC₁₂H₂₅, was synthesized by the reaction of the trithiocarbonate‐terminated PS with 2‐hydroxyethyl‐3‐(4‐(prop‐2‐ynyloxy)phenyl) acrylate (HEPPA) in tetrahydrofuran (THF) solution. Subsequently, the ring‐opening polymerization (ROP) of ε‐caprolactone (CL) was carried out in the presence of stannous(II) 2‐ethylhexanoate and PS‐HEPPA‐SC(S)SC₁₂H₂₅, and then the PS‐HEPPA(PCL)‐SC(S)SC₁₂H₂₅ obtained was used in reversible addition‐fragmentation chain transfer (RAFT) polymerization of methyl acrylate (MA) to produce the ABC 3‐miktoarm star polymer, S(PS)(PCL)(PMA) carrying an alkyne group. The ABCD 4‐miktoarm star polymer, S(PS)(PCL)(PMA)(PEO) was successfully prepared by click reaction of the alkyne group on the HEPPA unit with azide‐terminated PEO (PEO‐N₃). The target polymer and intermediates were characterized by NMR, FTIR, GPC, and DSC. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6641–6653, 2008     

Synthesis and characterization of pyrene bearing amphiphilic miktoarm star polymer and its noncovalent interactions with multiwalled carbon nanotubes

A novel amphiphilic miktoarm star polymer, polystyrene‐poly(ethylene glycol)‐poly(methyl methacrylate), bearing a pyrene group at the end of PS arm (Pyrene‐PS‐PEG‐PMMA) was successfully synthesized via combination of atom transfer radical polymerization and click chemistry. The structure and composition of the amphiphilic miktoarm star polymer were characterized by gel permeation chromatography and ¹H NMR. The functionalization of multiwalled carbon nanotubes (MWCNTs) via “π–π” stacking interactions with pyrene‐PS‐PEG‐PMMA miktoarm star polymer was accomplished and the resulting polymer‐MWCNTs hybrid was analyzed by using ¹H NMR, UV–vis, fluorescence spectroscopy, and thermal gravimetric analysis. The high‐resolution transmission electron microscopy and analytical techniques aforementioned confirmed that the noncovalent functionalization of MWCNT's with the amphiphilic miktoarm star polymer was successfully achieved. The MWCNT/pyrene‐PS‐PEG‐PMMA exhibited significant dispersion stability in common organic solvents such as dimethyl formamide, chloroform, and tetrahydrofuran. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Block and star block copolymers by mechanism transformation. IV. Synthesis of S‐(PSt)2(PDOP)2 miktoarm star copolymers by combination of ATRP and CROP

A new tetrafunctional initiator, di(hydroxyethyl)‐2,9‐dibromosebacate (DHEDBS) [HOCH₂CH₂OOCCHBr(CH₂)₆CHBrCOOCH₂CH₂OH], was synthesized and used in preparation of A₂B₂ miktoarm star copolymers, (polystyrene)₂/ [poly(1,3‐dioxepane)]₂ [S‐(PSt)₂(PDOP)₂], by transformation of atom transfer radical polymerization (ATRP) to cationic ring‐opening polymerization (CROP). First, two‐armed PSt with two primary hydroxyl groups sited at the center of macromolecule [(PStBr)₂(OH)₂] was obtained by ATRP of St with the initiation system of DHEDBS/CuBr/bpy, and used as a chain‐transfer agent in the CROP of DOP with triflic acid as the initiator. Therefore, A₂B₂ miktoarm star copolymer S‐(PSt)₂(PDOP)₂ was formed. Its structure was confirmed by the ¹H NMR spectrum. Gel permeation chromatography (GPC) curves show that the polymers obtained have a relatively narrow molecular weight distribution. The hydrolysis product of S‐(PSt)₂(PDOP)₂ was also characterized by ¹H NMR and GPC. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 437–445, 2001     

ABCD 4‐miktoarm star quarterpolymers using click [3 + 2] reaction strategy

Two samples of ABCD 4‐miktoarm star quarterpolymer with A = polystyrene (PS), B = poly(ε‐caprolactone) (PCL), C = poly(methyl methacrylate) (PMMA) or poly(tert‐butyl acrylate) (PtBA), and D = poly(ethylene glycol) (PEG) were prepared using click reaction strategy (Cu(I)‐catalyzed Huisgen [3 + 2] reaction). Thus, first, predefined block copolymers of different polymerization routes, PS‐b‐PCL with azide and PMMA‐b‐PEG and PtBA‐b‐PEG copolymers with alkyne functionality, were synthesized and then these blocks were combined together in the presence of Cu(I)/N,N,N′,N″,N″‐pentamethyldiethylenetriamine as a catalyst in DMF at room temperature to give the target 4‐miktoarm star quarterpolymers. The obtained miktoarm star quarter polymers were characterized by GPC, NMR, and DSC measurements. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 1218–1228, 2008     

Luminescent polymeric ruthenium complexes with polystyrene‐b‐poly(methyl methacrylate) macroligands: The sequential activation of initiator sites for blocks generated by parallel polymerization mechanisms

The synthesis of polystyrene‐b‐poly(methyl methacrylate) diblock copolymers with a luminescent ruthenium(II) tris(bipyridine) [Ru(bpy)₃] complex at the block junction is described. The macroligand precursor, polystyrene bipyridine‐poly(methyl methacrylate) [bpy(PS–H)(PMMA)], was synthesized via the atom transfer radical polymerization of styrene and methyl methacrylate from two independent, sequentially activated initiating sites. Both polymerization steps resulted in the growth of blocks with sizes consistent with monomer loading and narrow molecular weight distributions (i.e., polydispersity index < 1.3). Subsequent reactions with ruthenium(II) bis(bipyridine) dichloride [Ru(bpy)₂Cl₂] in the presence of Ag⁺ generated the ruthenium tris(bipyridine)‐centered diblock, which is of interest for the imaging of block copolymer microstructures and for incorporation into new photonic materials. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4250–4255, 2002     

Synthesis of ABCD‐type miktoarm star copolymers and transformation into zwitterionic star copolymers

ABCD‐type 4‐miktoarm star copolymers of styrene (St), α‐methylstyrene (αMSt), tert‐butyl methacrylate (tBuMA), and 4‐vinylpyridine (4VP) were synthesized via anionic polymerization using 1,3‐bis(1‐phenylvinyl)benzene (m‐DDPE) as the linking molecule. The synthetic route was rationally designed with respect to the reactivity of individual propagating anion towards the double bond of m‐DDPE. Thus the synthesis includes several consecutive key reactions, for example, the monoaddition of polystyryllithium towards m‐DDPE, the polymerization of tBuMA initiated by the resulting monoadduct to produce a diblock macromonomer, the coupling of the macromonomer with poly(α‐methylstyryl)lithium to form a 3‐arm star anion, and the polymerization of 4‐vinylpyridine initiated by the star anion. These reactions were conducted either in a one‐pot process, in which the diblock macromonomer was in situ coupled with poly(α‐methylstyryl)lithium, or in a batch polymerization process, in which the same diblock macromonomer was separated. The final product was hydrolyzed to produce a zwitterionic miktoarm star copolymer, which was soluble at lower pH but insoluble in neutral and basic solution. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4818–4828, 2007     

Miktoarm star copolymers of poly(ϵ‐caprolactone) from a novel heterofunctional initiator

A novel heterofunctional initiator, synthesized from pentaerythritol in a three step reaction sequence with two ring opening polymerization (ROP) and two atom transfer radical polymerization (ATRP) initiating sites, was used to prepare A₂B₂ miktoarm star copolymers of poly(ε‐caprolactone), PεCL, with polystyrene, PS, poly(methyl methacrylate), PMMA, poly(dimethylaminoethyl methacrylate), PDMAEMA, and poly(2‐hydroxyethyl methacrylate), PHEMA. A₂B miktoarm stars, A being PεCL or poly(δ‐valerolactone), PδVL and B PS were also prepared from ω,ω‐dihydroxy‐PS, synthesized from ω‐Br‐PS and serinol, by ROP of εCL or δVL. All polymers were characterized by size exclusion chromatography, ¹H NMR spectroscopy, and membrane osmometry. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5164–5181, 2007     

Heteroarm H‐shaped terpolymers through click reaction

Heteroarm H‐shaped terpolymers, (polystyrene)(poly(methyl methacrylate))‐ poly(tert‐butyl acrylate)‐(polystyrene)(poly(methyl methacrylate)), (PS)(PMMA)‐PtBA‐(PMMA)(PS), and, (PS)(PMMA)‐poly(ethylene glycol)(PEG)‐(PMMA)(PS), through click reaction strategy between PS‐PMMA copolymer (as side chains) with an alkyne functional group at the junction point and diazide end‐functionalized PtBA or PEG (as a main chain). PS‐PMMA with alkyne functional group was prepared by sequential living radical polymerizations such as the nitroxide mediated (NMP) and the metal mediated‐living radical polymerization (ATRP) routes. The obtained H‐shaped polymers were characterized by using ¹H‐NMR, GPC, DSC, and AFM measurements. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1055–1065, 2007     

Block copolymers based on 2‐vinyl‐4,4‐dimethyl‐5‐oxazolone by RAFT polymerization: Experimental and computational studies

The ability of 2‐vinyl‐4,4‐dimethyl‐5‐oxazolone (VDM), a highly reactive functional monomer, to produce block copolymers by reversible addition fragmentation chain transfer (RAFT) sequential polymerization with methyl acrylate (MA), styrene (S), and methyl methacrylate (MMA) was investigated using cumyl dithiobenzoate (CDB) and 2‐cyanoisopropyl dithiobenzoate (CPDB) as chain transfer agents. The results show that PS‐b‐PVDM and PMA‐b‐PVDM well‐defined block copolymers can be prepared either by polymerization of VDM from PS‐ and PMA‐macroCTAs, respectively, or polymerization of S and MA from a PVDM‐macroCTA. In contrast, PMMA‐b‐PVDM block copolymers with controlled molecular weight and low polydispersity can only be obtained by using PMMA as the macroCTA. Ab initio calculations confirm the experimental studies. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Stress–strain behavior of low‐density polyethylene/poly(methyl methacrylate) blends with modulated interfaces with a hydrogenated polybutadiene‐block‐poly(methyl methacrylate) diblock copolymer

The stress–strain diagrams and ultimate tensile properties of uncompatibilized and compatibilized hydrogenated polybutadiene‐block‐poly(methyl methacrylate) (HPB‐b‐PMMA) blends with 20 wt % poly(methyl methacrylate) (PMMA) droplets dispersed in a low‐density polyethylene (LDPE) matrix were studied. The HPB‐b‐PMMA pure diblock copolymer was prepared via controlled living anionic polymerization. Four copolymers, in terms of the molecular weights of the hydrogenated polybutadiene (HPB) and PMMA sequences (22,000–12,000, 63,300–31,700, 49,500–53,500, and 27,700–67,800), were used. We demonstrated with the stress–strain diagrams, in combination with scanning electron microscopy observations of deformed specimens, that the interfacial adhesion had a predominant role in determining the mechanism and extent of blend deformation. The debonding of PMMA particles from the LDPE matrix was clearly observed in the compatibilized blends in which the copolymer was not efficiently located at the interface. The best HPB‐b‐PMMA copolymer, resulting in the maximum improvement of the tensile properties of the compatibilized blend, had a PMMA sequence that was approximately half that of the HPB block. Because of the much higher interactions encountered in the PMMA phase in comparison with those in HPB (LDPE), a shorter sequence of PMMA (with respect to HPB but longer than the critical molecular weight for entanglement) was sufficient to favor a quantitative location of the copolymer at the LDPE/PMMA interface. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 22–34, 2005     

ABC type miktoarm star copolymers through combination of controlled polymerization techniques with thiol‐ene and azide‐alkyne click reactions

ABC type miktoarm star copolymer with polystyrene (PS), poly(ε‐caprolactone) (PCL) and poly(ethylene glycol) (PEG) arms was synthesized using controlled polymerization techniques in combination with thiol‐ene and copper catalyzed azide‐alyne “click” reactions (CuAAC) and characterized. For this purpose, 1‐(allyloxy)‐3‐azidopropan‐2‐ol was synthesized as the core component in a one‐step reaction with high yields (96%). Independently, ω‐thiol functionalized polystyrene (PS‐SH) was synthesized in a two‐step protocol with a very narrow molecular weight distribution. The bromo end function of PS obtained by atom transfer radical polymerization was first converted to xanthate function and then reacted with 1, 2‐ethandithiol to yield desired thiol functional polymer (PS‐SH). The obtained polymer was grafted onto the core by thiol‐ene click chemistry. In the following stage, ε‐caprolactone monomer was polymerized from the core by ring opening polymerization (ROP) using tin octoate as catalyst through hydroxyl groups to form the second arm. Finally, PEG‐acetylene, which was simply synthesized by the esterification of Me‐PEG and 5‐pentynoic acid, was clicked onto the core through azide groups present in the structure. The intermediates at various stages and the final miktoarm star copolymer were characterized by ¹H NMR, FTIR, and GPC measurements. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Block and star block copolymers by mechanism transformation X. Synthesis of poly(ethylene oxide) methyl ether/polystyrene/poly(l-lactide) ABC miktoarm star copolymers by combination of RAFT and ROP

Poly(ethylene oxide) methyl ether/polystyrene/poly(l-lactide) (MPEO/PSt/PLLA) ABC miktoarm star copolymers were synthesized by combination of reversible addition-fragmentation transfer (RAFT) polymerization and ring-opening polymerization (ROP) using bifunctional macro-transfer agent, MPEO with two terminal dithiobenzoate and hydroxyl groups. It was prepared by reaction of MPEO with maleic anhydride (MAh), subsequently reacted with dithiobenzoic acid and ethylene oxide. RAFT polymerization of St at 110 °C yielded block copolymer, MPEO-b-PSt [(MPEO)(PSt)CH₂OH], and then it was used to initiate the polymerization of l-lactide in the presence of Sn(OCt)₂ at 115 °C to produce ABC miktoarm star polymers, s-[(MPEO)(PSt)(PLLA)]. The structures of products obtained at each synthetic step were confirmed by NMR and gel permeation chromatography data.     

Micelles possessing mixed cores and thermoresponsive shells fabricated from well‐defined amphiphilic ABC miktoarm star terpolymers

Amphiphilic ABC miktoarm star terpolymers consisting of polystyrene, poly(ε‐caprolactone), and poly(N‐isopropylacrylamide) arms, PS(‐b‐PNIPAM)‐b‐PCL, were synthesized via a combination of atom transfer radical polymerization, ring‐opening polymerization (ROP), and click chemistry. Difunctional PS bearing an alkynyl and a primary hydroxyl moiety at the chain end, PS‐alknyl‐OH, was prepared by reacting azido‐terminated PS with an excess of 3,5‐bis(propargyloxy)benzyl alcohol (BPBA) under click conditions. The subsequent ROP of ε‐caprolactone using PS‐alknyl‐OH macroinitiator afforded PS(‐alkynyl)‐b‐PCL copolymer bearing an alkynyl moiety at the diblock junction point. Target PS(‐b‐PNIPAM)‐b‐PCL amphiphilic ABC miktoarm star terpolymers were then prepared via click reaction between PS(‐alkynyl)‐b‐PCL and an excess of azido‐terminated PNIPAM (PNIPAM‐N₃). The removal of excess PNIPAM‐N₃ was accomplished by “clicking” onto alkynyl‐functionalized Wang resin. All the intermediate and final products were characterized by gel permeation chromatography, ¹H NMR, and FTIR. In aqueous solution, the obtained amphiphilic ABC miktoarm star terpolymer self‐assembles into micelles possessing mixed PS/PCL cores and thermoresponsive shells, which were further characterized by dynamic laser light scattering and transmission electron microscopy. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 1636–1650, 2009     

Compatibilizing effect of a graft copolymer on bacterial poly(3‐hydroxybutyrate)/poly(methyl methacrylate) blends

Blends of isotactic (natural) poly(3‐hydroxybutyrate) (PHB) and poly(methyl methacrylate) (PMMA) are partially miscible, and PHB in excess of 20 wt % segregates as a partially crystalline pure phase. Copolymers containing atactic PHB chains grafted onto a PMMA backbone are used to compatibilize phase‐separated PHB/PMMA blends. Two poly(methyl methacrylate‐g‐hydroxybutyrate) [P(MMA‐g‐HB)] copolymers with different grafting densities and the same length of the grafted chain have been investigated. The copolymer with higher grafting density, containing 67 mol % hydroxybutyrate units, has a beneficial effect on the mechanical properties of PHB/PMMA blends with 30–50% PHB content, which show a remarkable increase in ductility. The main effect of copolymer addition is the inhibition of PHB crystallization. No compatibilizing effect on PHB/PMMA blends with PHB contents higher than 50% is observed with various amounts of P(MMA‐g‐HB) copolymer. In these blends, the graft copolymer is not able to prevent PHB crystallization, and the ternary PHB/PMMA/P(MMA‐g‐HB) blends remain crystalline and brittle. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1390–1399, 2002     

Synthesis of coil‐comb block copolymers containing polystyrene coil and poly(methyl methacrylate) side chains via atom transfer radical polymerization

A series of polystyrene‐b‐(poly(2‐(2‐bromopropionyloxy) styrene)‐g‐poly(methyl methacrylate)) (PS‐b‐(PBPS‐g‐PMMA)) and polystyrene‐b‐(poly(2‐(2‐bromopropionyloxy)ethyl acrylate)‐g‐poly(methyl methacrylate)) (PS‐b‐(PBPEA‐g‐PMMA)) as new coil‐comb block copolymers (CCBCPs) were synthesized by atom transfer radical polymerization (ATRP). The linear diblock copolymer polystyrene‐b‐poly(4‐acetoxystyrene) and polystyrene‐b‐poly(2‐(trimethylsilyloxy)ethyl acrylate) PS‐b‐P(HEA‐TMS) were obtained by combining ATRP and activators regenerated by electron transfer (ARGET) ATRP. Secondary bromide‐initiating sites for ATRP were introduced by liberation of hydroxyl groups via deprotection and subsequent esterification reaction with 2‐bromopropionyl bromide. Grafting of PMMA onto either the PBPS block or the PBPEA block via ATRP yielded the desired PS‐b‐(PBPS‐g‐PMMA) or PS‐b‐(PBPEA‐g‐PMMA). ¹H nuclear magnetic resonance spectroscopy and gel permeation chromatography data indicated the target CCBCPs were successfully synthesized. Preliminary investigation on selected CCBCPs suggests that they can form ordered nanostructures via microphase separation. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 2971–2983     

Thermo‐responsive fluorescent micelles from amphiphilic A3B miktoarm star copolymers prepared via a combination of SET‐LRP and RAFT polymerization

A novel amphiphilic A₃B miktoarm star copolymer poly(N‐isopropylacrylamide)₃‐poly(N‐vinylcarbazole) ((PNIPAAM)₃(PVK)) was successfully synthesized by a combination of single‐electron transfer living radical polymerization (SET‐LRP) and reversible addition‐fragmentation chain transfer (RAFT) polymerization. First, the well‐defined three‐armed poly(N‐isopropylacrylamide) (PNIPAAM)₃ was prepared via SET‐LRP of N‐isopropylacrylamide in acetone at 25 °C using a tetrafunctional bromoxanthate iniferter (Xanthate‐Br₃) as the initiator and Cu(0)/PMDETA as a catalyst system. Secondly, the target amphiphilic A₃B miktoarm star copolymer ((PNIPAAM)₃(PVK)) was prepared via RAFT polymerization of N‐vinylcarbazole (NVC) employing (PNIPAAM)₃ as the macro‐RAFT agent. The architecture of the amphiphilic A₃B miktoarm star copolymers were characterized by GPC, ¹H‐NMR spectra. Furthermore, the fluorescence intensity of micelle increased with the temperature and had a good temperature reversibility, which was investigated by dynamic light scattering (DLS), fluorescent and UV‐vis spectra. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 4268–4278, 2010     

H‐shaped (ABCDE type) quintopolymer via click reaction [3 + 2] strategy

H‐shaped quintopolymer containing different five blocks: poly(ε‐caprolactone) (PCL), polystyrene (PS), poly(ethylene glycol) (PEG), and poly(methyl methacrylate) (PMMA) as side chains and poly(tert‐butyl acrylate) (PtBA) as a main chain was simply prepared from a click reaction between azide end‐functionalized PCL‐PS‐PtBA 3‐miktoarm star terpolymer and PEG–PMMA‐block copolymer with alkyne at the junction point, using Cu(I)/N,N,N′,N″,N″‐pentamethyldiethylenetriamine (PMDETA) as a catalyst in DMF at room temperature for 20 h. The H‐shaped quintopolymer was obtained with a number–average molecular weight (M_n) around 32,000 and low polydispersity index (M_w/M_n) 1.20 as determined by GPC analysis in THF using PS standards. The click reaction efficiency was calculated to have 60% from ¹H NMR spectroscopy. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4459–4468, 2008     

Facile synthesis for well‐defined A2B miktoarm star copolymer of poly(3‐hexylthiophene) and poly(methyl methacrylate) by the combination of anionic polymerization and click reaction

We have introduced a facile synthetic route for well‐defined A₂B miktoarm star copolymer composed of regioregular poly(3‐hexylthiophene) and poly(methyl methacrylate) ((P3HT)₂PMMA) by the combination of anionic polymerization and click reaction. First, we synthesized PMMA terminated with 1,3,5‐tris(bromomethyl)benzene (PMMA‐(Br)₂) by anionic polymerization, and two bromines attached to the end of the PMMA chains were replaced by azides (PMMA‐(N₃)₂). Also, monoethynyl‐capped P3HT was synthesized by Grignard metathesis polymerization and post‐end functionalization. Then, copper(I)‐catalyzed Huisgen 1,3‐dipolar cycloaddition click reaction between monoethynyl‐capped P3HT and PMMA‐(N₃)₂ was performed to synthesize (P3HT)₂PMMA. We used a slightly excess amount of monoethynyl‐capped P3HT so that all of the azide groups at the end of the PMMA chains completely reacted with monoethynyl‐capped P3HT. After complete removal of unreacted monoethynyl‐capped P3HT by column chromatography, pure (P3HT)₂PMMA with narrow molecular weight distribution (the polydispersity of 1.18) was obtained. The weight fraction of P3HT and the total molecular weight of (P3HT)₂PMMA are 0.48 and 16,000, respectively. To investigate the effect of the chain architecture on optical property and thin‐film morphology, we synthesized two linear P3HT‐b‐PMMAs (P3HT‐b‐PMMA‐L and P3HT‐b‐PMMA‐H) with similar weight fraction of P3HT block (0.48 for P3HT‐b‐PMMA‐L and 0.45 for P3HT‐b‐PMMA‐H) but two different total molecular weights (7900 for P3HT‐b‐PMMA‐L and 15,300 for P3HT‐b‐PMMA‐H). UV–visible (UV–vis) absorption spectrum and the fibril width of (P3HT)2PMMA thin film were similar to those of P3HT‐b‐PMMA‐L thin film. However, UV–vis spectrum for P3HT‐b‐PMMA‐H thin film was red‐shifted and the fibril width of P3HT‐b‐PMMA‐H was much larger than that of (P3HT)₂PMMA. This indicates that the π–π interaction between P3HT arms in (P3HT)₂PMMA is strong enough to arrange two P3HT backbone chains in (P3HT)₂PMMA to stack one by one along the nanofibril axis. © 2013 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013