Novel block ionomers. I. Synthesis and characterization of polyisobutylene‐based block anionomers

A series of novel block anionomers consisting of polyisobutylene (PIB) and poly(methacrylic acid) (PMAA) segments were prepared and characterized. The specific targets were various molecular weight diblocks (PIB‐b‐PMAA^?), triblocks (PMAA^?‐b‐PIB‐b‐PMAA^?), and three‐arm star blocks [Φ(PIB‐b‐PMAA^?)₃] consisting of rubbery PIB blocks with a number‐average degree of polymerization of 50–1000 (number‐average molecular weight = 3000–54,000 g/mol) connected to blocks of PMAA^? anions with a number‐average degree of polymerization of 5–20. The overall strategy for the synthesis of these constructs consisted of four steps: (1) synthesis by living cationic polymerization of t‐chloro‐monotelechelic, t‐chloro‐ditelechelic, and t‐chloro‐tritelechelic PIBs; (2) site transformation to obtain PIBs fitted with termini capable of mediating the atom transfer radical polymerization (ATRP) of tert‐butyl methacrylate (tBMA); (3) ATRP of tBMA, and (4) hydrolysis of poly(tert‐butyl methacrylate) to PMAA^?. The architectures created and the synthesis steps employed are summarized. Kinetic and model experiments greatly assisted in the development of convenient synthesis methods. The microarchitectures of the various block anionomers were confirmed by spectroscopy and other techniques. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3662–3678, 2002     

An insight into the schizophrenic self‐assembly of thermo and proton sensitive graphene oxide grafted block copolymer

In order to study the self‐assembly of block copolymer grafted from graphene oxide (GO) by the fluorescence of GO, poly(ε‐caprolactone) (PCL)‐block‐poly(dimethyl aminoethyl methacrylate) (PDMAEMA) is grafted from its surface using consecutive ring opening (ROP) and atom transfer radical polymerization (ATRP). GO‐g‐(PCL₁₃‐b‐PDMAEMA₁₁₇) (GPCLD) at pH 9.2 exhibits cloud point (T_c) at 32 °C. At pH 9.2 HRTEM images indicate schizophrenic morphology from vesicle at 26 °C to annular ring at 30 °C followed by giant size aggregation at 38 °C. But the reference block copolymer (PCL₁₄‐b‐PDMAEMA₁₂₆, PCLD), synthesized using benzyl alcohol as ROP initiator, exhibits only core–shell morphology whose size increases with rising temperature at pH 9.2. GPCLD solution exhibits good photoluminescence (PL) property arising from GO at pH 9.2 and PL‐intensity increases abruptly during phase transition. Both T_c and size of GPCLD assembly can be reversibly tuned by CO₂ and N₂ gas purging. ¹H NMR spectra exhibit a gradual shift of resonance peaks of the protons on CO₂ bubbling. Thus at pH 9.2 and at 38 °C the GPCLD acts as a good CO₂ sensor. Additionally, the GPCLD vesicle can load hydrophobic guest molecules which can be released by triggering with CO₂. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 3878–3887     

Star–block polymers of multiple polystyrene-b-polyisobutylene arms radiating from a polydivinylbenzene core

The synthesis together with mechanical property and rheological characterization of novel star–block copolymers comprising multiple polystyrene (PSt)-b-polyisobutylene (PIB) arms emanating from polydivinylbenzene (PDVB) cores are described. The synthesis strategy involved the preparation of PSt-b-PIB-Cl^t (i.e., diblocks fitted with a tert-chlorine terminus at the PIB end) by sequential living block polymerization of St and IB, ionizing the -Cl^t terminus by TiCl₄ at room temperature, and linking the PSt-b-PIB^⊕ prearms by DVB. Molecular characterization was effected mainly by triple detector GPC including refractive index (RI)-, UV-, and laser light scattering (LLS)-GPC traces. Evidence for intra- and intermolecular reactions between individual star–blocks is presented and a comprehensive mechanism to the final product is proposed. The stress–strain behavior of star–blocks has been studied and is compared with those of linear triblocks (i.e., two-arm stars) of similar arm molecular weights and composition in the 25–70°C range. The mechanical properties of star–blocks are invariably superior to those of the triblocks over the entire temperature range. The rheological behavior of star–blocks and linear triblocks has been compared in terms of dynamic viscosity at various frequencies. Star–blocks exhibit significantly lower melt viscosities than their linear counterparts, which signals improved processing behavior. We have also compared select rheological properties of the commercially available PSt-b-(hydrogenated-1,4-polybutadiene)-b-PSt thermoplastic elastomer (Kraton G 1650) with those of PIB-based linear triblocks and multiarm star–blocks of similar glassy/rubbery compositions. The melt viscosities of PIB-based triblocks and star–blocks were significantly lower than that of Kraton G over the entire frequency range investigated. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 2235–2243, 1999     

Amphiphilic diblock,triblock, and star block copolymers by living radical polymerization: Synthesis and aggregation behavior

Copper(I)‐mediated living radical polymerization was used to synthesize amphiphilic block copolymers of poly(n‐butyl methacrylate) [P(n‐BMA)] and poly[(2‐dimethylamino)ethyl methacrylate] (PDMAEMA). Functionalized bromo P(n‐BMA) macroinitiators were prepared from monofunctional, difunctional, and trifunctional initiators: 2‐bromo‐2‐methylpropionic acid 4‐methoxyphenyl ester, 1,4‐(2′‐bromo‐2′‐methyl‐propionate)benzene, and 1,3,5‐(2′‐bromo‐2′‐methylpropionato)benzene. The living nature of the polymerizations involved was investigated in each case, leading to narrow‐polydispersity polymers for which the number‐average molecular weight increased fairly linearly with time with good first‐order kinetics in the monomer. These macroinitiators were subsequently used for the polymerization of (2‐dimethylamino)ethyl methacrylate to obtain well‐defined [P(n‐BMA)_x‐b‐PDMAEMA_y]_z diblock (15,900; polydispersity index = 1.60), triblock (23,200; polydispersity index = 1.24), and star block copolymers (50,700; polydispersity index = 1.46). Amphiphilic block copolymers contained between 60 and 80 mol % hydrophilic PDMAEMA blocks to solubilize them in water. The polymers were quaternized with methyl iodide to render them even more hydrophilic. The aggregation behavior of these copolymers was investigated with fluorescence spectroscopy and dynamic light scattering. For blocks of similar comonomer compositions, the apparent critical aggregation concentration (cac = 3.22–7.13 × 10^?3 g L^?1) and the aggregate size (ca. 65 nm) were both dependent on the copolymer architecture. However, for the same copolymer structure, increasing the hydrophilic PDMAEMA block length had little effect on the cac but resulted in a change in the aggregate size. © 2002 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 40: 439–450, 2002; DOI 10.1002/pola.10122     

Dual‐responsive supramolecular inclusion complexes of block copolymer poly(ethylene glycol)‐block‐poly[(2‐dimethylamino)ethyl methacrylate] with α‐cyclodextrin

A new class of temperature and pH dual‐responsive and injectable supramolecular hydrogel was developed, which was formed from block copolymer poly(ethylene glycol)‐block‐poly[(2‐dimethylamino)ethyl methacrylate] (PEG‐b‐PDMAEMA) and α‐cyclodextrin (α‐CD) inclusion complexes (ICs). The PEG‐b‐PDMAEMA diblock copolymers with different ratio of ethylene glycol (EG) to (2‐dimethylamino)ethyl methacrylate (DMAEMA) (102:46 and 102:96, respectively) were prepared by atom transfer radical polymerization (ATRP). ¹H NMR measurement indicated that the ratio of EG unit to α‐CD in the resulted ICs was higher than 2:1. Thermal analysis showed that thermal stability of ICs was improved. The rheology studies showed that the hydrogels were temperature and pH sensitive. Moreover, the hydrogels were thixotropic and reversible. The self‐assembly morphologies of the ICs in different pH and ionic strength environment were studied by transmission electron microscopy. The formed biocompatible micelles have potential applications as biomedical and stimulus‐responsive material. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2143–2153, 2010     

Thermal and pH‐sensitive gold nanoparticles from H‐shaped block copolymers of (PNIPAM/PDMAEMA)‐b‐PEG‐b‐(PNIPAM/PDMAEMA)

Well‐defined H‐shaped pentablock copolymers composed of poly(N‐isopropylacrylamide) (PNIPAM), poly(N,N‐dimethylaminoethylacrylamide) (PDMAEMA), and poly(ethylene glycol) (PEG) with the chain architecture of (A/B)‐b‐C‐b‐(A/B) were synthesized by the combination of single‐electron‐transfer living radical polymerization, atom‐transfer radical polymerization, and click chemistry. Single‐electron‐transfer living radical polymerization of NIPAM using α,ω azide‐capped PEG macroinitiator resulted in PNIPAM‐b‐PEG‐b‐PNIPAM with azide groups at the block joints. Atom‐transfer radical polymerization of DMAEMA initiated by propargyl 2‐chloropropionate gave out α‐capped alkyne‐PDMAEMA. The H‐shaped copolymers were finally obtained by the click reaction between PNIPAM‐b‐PEG‐b‐PNIPAM and alkyne‐PDMAEMA. These copolymers were used to prepare stable colloidal gold nanoparticles (GNPs) in aqueous solution without any external reducing agent. The formation of GNPs was affected by the length of PDMAEMA block, the feed ratio of the copolymer to HAuCl₄, and the pH value. The surface plasmon absorbance of these obtained GNPs also exhibited pH and thermal dependence because of the existence of PNIAPM and PDAMEMA blocks. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Peptide‐poly(2‐(dimethylamino)ethyl methacrylate) conjugates: Synthesis and aqueous/nonaqueous self‐aggregation into nanostructures of dendritic and spherical morphologies

Peptide–polymer conjugate consisting of a sequence‐defined tripeptide and poly(2‐(dimethylamino)ethyl methacrylate) (PDMAEMA) is synthesized by a simple “grafting from” atom transfer radical polymerization (ATRP) approach. The ATRP of PDMAEMA using peptide‐macroinitiator and CuBr/1,1,4,7,10,10‐hexamethyltriethylenetetramine system in anisole follows pseudo first order kinetics up to a conversion of about 25% within a time span of 125 min. The attachment of peptide moiety at the end of PDMAEMA chain is confirmed from MALDI‐TOF‐MS and circular dichroism analyses. The self‐assembly of as‐synthesized peptide‐PDMAEMA conjugate in organic solvents leads to the formation of spherical nanoparticles as observed through FESEM. Peptide‐PDMAEMA conjugate become soluble in water due to the protonation of the pendent —N(CH₃)₂ moiety of DMAEMA group of the conjugate. Owing to the amphiphilic nature of the protonated conjugate (peptide‐PDMAEMAH), it also undergoes self‐aggregation in water into nanostructures of various morphologies such as dendrite, small sphere and large sphere at pHs of 2, 8, and 10, respectively. Peptide‐PDMAEMA‐IBu conjugate obtained by the post‐modification of —N(CH₃)₂ moiety of DMAEMA group of the conjugate with n‐butylbromide also undergoes self‐aggregation into dendritic nanostructures in water. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 3286–3297     

Synthesis of azobenzene‐containing polymers via RAFT polymerization and investigation on intense fluorescence from aggregates of azobenzene‐containing amphiphilic diblock copolymers

The well‐defined azobenzene‐containing homopolymers, poly{6‐(4‐phenylazophenoxy)hexyl methacrylate (AHMA)} (PAHMA), were synthesized via reversible addition fragmentation chain transfer polymerization (RAFT) in anisole solution using 2‐cyanoprop‐2‐yl 1‐dithionaphthalate (CPDN) as the RAFT agent and 2,2′‐azobisisobutyronitrile (AIBN) as the initiator. The first‐order kinetic plot of the polymerization and the linear dependence of molecular weights of the homopolymers with the relatively low polydispersity index values (PDIs ≤ 1.25) on the monomer conversions were observed. Furthermore, the amphiphilic diblock copolymer, poly{6‐(4‐phenylazophenoxy)hexyl methacrylate (AHMA)}‐b‐poly{2‐(dimethylamino)ethyl methacrylate (DMAEMA)} (PAHMA‐b‐PDMAEMA), was prepared with the obtained PAHMA as the macro‐RAFT agent. The structures and properties of the polymers were characterized by ¹H NMR and GPC, respectively. Interestingly, the amphiphilic diblock copolymers in chloroform (CHCl₃) solution (PAHMA₂₃‐b‐PDMAEMA₉₇ (4 × 10^?5 M, M_n(GPC) = 18,400 g/mol, PDI = 1.48) and PAHMA₂₈‐b‐PDMAEMA₁₁₇ (6 × 10^?5 M, M_n(GPC) = 19,300 g/mol, PDI = 1.51) exhibited the intense fluorescence emission at ambient temperature. Moreover, the fluorescent intensity of PAHMA‐b‐PDMAEMA in CHCl₃ was sensitive to the ultraviolet irradiation at 365 nm, which increased within the first 10 min and later decreased when irradiation time was prolonged to 30 min or longer. The well distributed, self‐assembled micelles composed of azobenzene‐containing amphiphilic diblock copolymers, (PAHMA‐b‐QPDMAEMA)s (QPDMAEMA is quaternized PDMAEMA), in the mixed N,N‐dimethyl formamide (DMF)/H₂O solutions were prepared. Their fluorescent intensities decreased with the increasing amount of water. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5652–5662, 2008     

Novel star‐block polymers: Three polyisobutylene‐b‐poly(methyl methacrylate) arms radiating from an aromatic core

A series of novel three‐arm star blocks consisting of three polyisobutylene‐b‐poly(methyl methacrylate) (PIB‐b‐PMMA) diblocks radiating from a tricumyl core were synthesized, characterized, and tested. The synthetic strategy involved three steps: the synthesis of Cl^t ‐tritelechelic PIB by living cationic isobutylene (IB) polymerization, the conversion of the Cl^t termini to isobutyryl bromide groups, and the initiation of living radical methyl methacrylate (MMA) polymerization by the latter groups. The PIB and PMMA segment lengths (M_n 's) could be controlled by controlling the conditions of the living cationic and radical polymerizations of IB and MMA, respectively. Core destruction analysis directly proved the postulated three‐arm microarchitecture. The structures of the products were analyzed by ¹H NMR and Fourier transform infrared spectroscopies, and their thermal properties were analyzed by differential scanning calorimetry and thermogravimetric analysis. The presence of a low‐ and a high‐temperature glass transition (T_g,PIB ∼ −63°C, T_g,PMMA ∼ 120°C) indicated a phase‐separated micromorphology. Stress/strain analysis showed a tensile strength of up to ∼ 22.9 MPa and an elongation of ∼ 200%. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 706–714, 2000     

Novel thermoplastic elastomers. II. Properties of star‐block copolymers of PSt‐b‐PIB arms emanating from cyclosiloxane cores

Select mechanical, thermal, and rheological properties of star‐blocks consisting of 5–21 polystyrene‐b‐polyisobutylene (PSt‐b‐PIB) arms radiating from cyclosiloxane cores are described. The tensile properties of products containing 23–41 wt % of PSt are substantially higher (9.6–23.8 MPa) than those of linear triblocks of comparable arm molecular weights and compositions over the 25–85°C temperature range. The mechanical properties of star‐blocks seem to be much less sensitive to diblock contamination than linear triblock thermoplastic elastomers of similar hard/soft segment composition. The tensile strength of star‐blocks increases by increasing the number of arms (N_w,arm) and reaches a plateau in the N_w,arm = 5–10 range. Star‐blocks exhibit higher strengths with lower PSt segmental M_n than linear triblocks. Solvent cast triblock copolymers exhibit higher tensile strengths than compression molded products; however, star‐blocks show no significant property differences between cast and molded samples. The dynamic melt viscosities of the star‐blocks are substantially lower than those of linear triblocks with comparable hard/soft segment compositions, which is consistent with the star's unique microarchitecture and should lead to improved overall processibility. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 815–824, 1999     

Amphiphilic β‐cyclodextrin‐based star‐like block copolymer unimolecular micelles for facile in situ preparation of gold nanoparticles

Multifunctional polymer unimolecular micelles, which are used as templates to fabricate stable gold nanoparticles (GNPs) in one‐step without external reductant, have been designed and prepared. Amphiphilic 21‐arm star‐like block copolymers β‐cyclodextrin‐{poly(lactide)‐poly(2‐(dimethylamino) ethyl methacrylate)‐poly[oligo(2‐ethyl‐2‐oxazoline)methacrylate]}₂₁ [β‐CD‐(PLA‐PDMAEMA‐PEtOxMA)₂₁] and the precursors are synthesized by the combination of ring‐opening polymerization (ROP) and activators regenerated by electron transfer atom transfer radical polymerization (ARGET ATRP). The tertiary amine groups of PDMAEMA block reduce the counterion to zerovalent gold in situ, and these gold atoms combine mutually to form final GNPs. GNPs with relatively small size and narrow size distribution can be obtained in longer DMAEMA block copolymer, larger molar ratio of DMAEMA to HAuCl₄ and smaller absolute concentrations of both polymer and HAuCl₄. These results showed that the unimolecular micelles can be used as templates for preparing and stabilizing GNPs in situ without any external reducing agents and organic solvents, suggesting that the nanocomposite systems are latent nanocarriers for further biomedical application. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 186–196     

Preparation of amphiphilic ternary block copolymers with PEO as the middle block and the effect of PEO position on the glass transition temperature (Tg) of copolymers

The copolymer of polystyrene‐block‐poly(ethylene oxide)‐block‐poly (tert‐butyl acrylate) (PS‐b‐PEO‐b‐PtBA) was prepared, the synthesis process involved ring‐opening polymerization (ROP), nitroxide‐mediated polymerization (NMP), and atom transfer radical polymerization (ATRP), and 4‐hydroxyl‐2,2,6,6‐tetramethylpiperidinyl‐1‐oxy (HTEMPO) was used as parent compound. The PEO precursors with α‐hydroxyl‐ω‐2,2,6,6‐tetramethylpiperidinyl‐1‐oxy end groups(TEMPO‐PEO‐OH) were first obtained by ROP of EO using HTEMPO and diphenylmethylpotassium (DPMK) as the coinitiator. The TEMPO at one end of PEO chain mediated the polymerization of St using benzoyl peroxide as initiator. The resultant PS‐b‐PEO‐OH reacted further with 2‐bromoisobutyryl bromide and then initiated the polymerization of tBA in the presence of CuBr and PMDETA by ATRP. The ternary block copolymers PS‐b‐PEO‐b‐PtBA and intermediates were characterized by gel permeation chromatography, Fourier transform infrared, and nuclear magnetic resonance spectroscopy in detail. Differential scanning calorimetry measurements confirmed that the PS‐b‐PEO‐b‐PtBA with PEO as middle block can weaken the interaction between PS and PtBA blocks, the glass transition temperature (T_g) for two blocks were approximate to their corresponding homopolymers comparing with the PEO‐b‐PS‐b‐PtBA with PEO as the first block. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2624–2631, 2008     

Temperature and pH dual stimuli responsive PCL‐b‐PNIPAAm block copolymer assemblies and the cargo release studies

A new atom transfer radical polymerization (ATRP) initiator, namely, 2‐(1‐(2‐azidoethoxy)ethoxy)ethyl 2‐bromo‐2‐methylpropanoate containing both “cleavable” acetal linkage and “clickable” azido group was synthesized. Well‐defined azido‐terminated poly(N‐isopropylacrylamide)s (PNIPAAm‐N₃)s with molecular weights and dispersity in the range 11,000–19,000 g mol^?1 and 1.20–1.28, respectively, were synthesized employing the initiator by ATRP. Acetal containing PCL‐b‐PNIPAAm block copolymer was obtained by alkyne–azide click reaction of azido‐terminated PNIPAAm‐N₃ with propargyl‐terminated PCL. Critical aggregation concentration (CAC) of PCL‐b‐PNIPAAm copolymer in aqueous solution was found to be 8.99 × 10^?6 M. Lower critical solution temperature (LCST) of PCL‐b‐PNIPAAm copolymer was found to be 32 °C which was lower than that of the precursor PNIPAAm‐N₃ (36.4 °C). The effect of dual stimuli viz . temperature and pH on size and morphology of the assemblies of PCL‐b‐PNIPAAm block copolymer revealed that the copolymer below LCST assembled in spherical micelles which subsequently transformed to unstable vesicles above the LCST. Heating these assemblies above 40 °C led to the precipitation of PCL‐b‐PNIPAAm block copolymer. Whereas, at decreased pH, micelles of PCL‐b‐PNIPAAm copolymer disintegrate due to the cleavage of acetal linkage and precipitation of hydrophobic hydroxyl‐terminated PCL. The encapsulated pyrene release kinetics from the micelles of synthesized PCL‐b‐PNIPAAm copolymer was found to be faster at higher temperature and at lower pH. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55 , 1383–1396     

Synthesis and characterization of two novel star blocks: tCum[poly(isobutylene‐b‐norbornadiene)]3 and tCum[poly(norbornadiene‐b‐isobutylene)]3

Two structurally closely related three‐arm star blocks were synthesized and characterized: tCum(PIB‐b‐PNBD)₃ and tCum(PNBD‐b‐PIB)₃ [where tCum (tricumyl) stands for the phenyl‐1,3,5‐tris(‐2‐propyl) fragment and PIB and PNBD are polyisobutylene and polynorbornadiene, respectively]. The syntheses were accomplished in two stages: (1) the preparation of the first (or inner) block fitted with appropriate chlorine termini capable of initiating the polymerization of the second (or outer) block with TiCl₄ and (2) the mediation of the polymerization of the second block. Therefore, the synthesis of tCum(PIB‐b‐PNBD)₃ was effected with tCum(PIB‐Cl^t)₃ [where Cl^t is tert‐chlorine and number‐average molecular weight (M_n) = 102,000 g/mol] by the use of TiCl₄ and 30/70 CH₃Cl/CHCl₃ solvent mixtures at ?35 °C. PNBD homopolymer contamination formed by chain transfer was removed by selective precipitation. According to gel permeation chromatography, the M_n's of the star blocks were 107,300–109,200 g/mol. NMR spectroscopy (750 MHz) was used to determine structures and molecular weights. Differential scanning calorimetry (DSC) indicated two glass‐transition temperatures (T_g's), one each for the PIB (?65 °C) and PNBD (232 °C) phases. Thermogravimetric analysis thermograms showed 5% weight losses at 293 °C in air and at 352 °C in N₂. The synthesis of tCum(PNBD‐b‐PIB)₃ was achieved by the initiation of isobutylene polymerization with tCum(PNBD‐Cl^sec)₃ (where Cl^sec is sec‐chlorine and M_n = 2900 g/mol) by the use of TiCl₄ in CH₃Cl at ?60 °C. DSC for this star block (M_n = 14,200 g/mol) also showed two T_g's, that is, at ?67 and 228 °C for the PIB and PNBD segments, respectively. It is of interest that the Cl^sec terminus of PNBD, , readily initiated isobutylene polymerization. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 740–751, 2003     

Synthesis and characterization of novel dendritic (arborescent,hyperbranched) polyisobutylene–polystyrene block copolymers

The synthesis of novel arborescent (arb; randomly branched, “tree‐like,” and often called “hyperbranched”) block copolymers comprised of rubbery polyisobutylene (PIB) and glassy polystyrene (PSt) blocks (arb‐PIB‐b‐PSt) is described. The syntheses were accomplished by the use of arb‐PIB macroinitiators (prepared by the use of 4‐(2‐methoxyisopropyl) styrene inimer) in conjunction with titanium tetrachloride (TiCl₄). The effect of reaction conditions on blocking of St from arb‐PIB was investigated. Purified block copolymers were characterized by ¹H NMR spectroscopy and Size Exclusion Chromatography (SEC). arb‐PIB‐b‐PSt with 11.7–33.8 wt % PSt and M_n = 468,800–652,900 g/mol displayed thermoplastic elastomeric properties with 3.6–8.7 MPa tensile strength and 950–1830% elongation. Samples with 26.8–33.8 wt % PSt were further characterized by Atomic Force Microscopy (AFM), which showed phase‐separated mixed spherical/cylindrical/lamellar PSt phases irregularly distributed within the continuous PIB phase. Dynamic Mechanical Thermal Analysis (DMTA) and solvent swelling of arb‐PIB‐b‐PSt revealed unique characteristics, in comparison with a semicommercial PSt‐b‐PIB‐b‐PSt block copolymer. The number of aromatic branching points of the arb‐PIB macroinitiator, determined by selective destruction of the linking sites, agreed well with that calculated from equilibrium swelling data of arb‐PIB‐b‐PSt. This method for the quantitative determination of branching sites might be generally applicable for arborescent polymers. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1811–1826, 2005     

Synthesis of nitroxide‐containing block copolymers for the formation of organic cathodes

This contribution describes the polymerization of 2,2,6,6‐tetramethylpiperidin‐4‐yl methacrylate by atom transfer radical polymerization (ATRP). Different catalytic systems are compared. The CuCl/4,4′‐dinonyl‐2,2′‐dipyridyl catalytic system allows a good control over the polymerization and provides polymers with a polydispersity index below 1.2. The successful polymerization of styrene from PTMPM‐Cl macroinitiators by ATRP is then demonstrated. Successful quantitative oxidation of PTMPM‐b‐PS block copolymers leads to poly(2,2,6,6‐tetramethylpiperidinyloxy‐4‐yl‐methacrylate)‐b‐poly(styrene) (PTMA‐b‐PS). The cyclic voltammogram of PTMA‐b‐PS indicates a reversible redox reaction at 3.6 V (vs. Li⁺/Li). Such block copolymers open new opportunities for the formation of functional organic cathode materials. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

One‐pot synthesis of block copolymers by ring‐opening polymerization and ultraviolet light‐induced ATRP at ambient temperature

We successfully synthesized poly(l ‐lactide)‐b‐poly (methyl methacrylate) diblock copolymers at ambient temperature by combining ultraviolet light‐induced copper‐catalyzed ATRP and organo‐catalyzed ring‐opening polymerization (ROP) in one‐pot. The polymerization processes were carried out by three routes: one‐pot simultaneous ATRP and ROP, one‐pot sequential ATRP followed by ROP, and one‐pot sequential ROP followed by ATRP. The structure of the block copolymers is confirmed by nuclear magnetic resonance and gel permeation chromatography, which suggests that the polymerization method is facile and attractive for preparing block copolymers. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 699–704     

Dual‐responsive copolymer poly(2,2,3,4,4,4‐hexafluorobutyl methacrylate)‐block‐poly[2‐(dimethylamino)ethyl methacrylate] synthesized via photoATRP for surface with tunable wettability

In this work, a series of block copolymers of poly(2,2,3,4,4,4‐hexafluorobutyl methacrylate)‐block‐poly[2‐(dimethylamino)ethyl methacrylate] (PHFBMA‐b‐PDMAEMA) were synthesized via photo‐induced atom transfer radical polymerization (photoATRP) at room temperature. By the introduction of PDMAEMA segment, the hydrophilicity of the silicon wafer surface spin‐coated with PHFBMA homopolymer was improved. Furthermore, the study of tunable surface wettability showed that the surface wettability was pH‐dependent and thermal‐independent at pH 2 and 10. The as‐fabricated surface coated with PHFBMA₁₁₀‐b‐PDMAEMA₁₈₇ showed switchable water contact angle from 85.4° at pH > 4 to 55.0° at pH 2 due to the protonation and deprotonation of tertiary amine groups of PDMAEMA. However, because of the ascendancy of protonated PDMAEMA at pH 2 and the decreased LCST at pH 10, the wettability of the as‐prepared surfaces was thermal‐insensitive. Finally, surface morphology and composition investigation showed that the property of wettability‐controllable surface was not only influenced by surface composition, but also affected by chain conformation. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 3868–3877     

Synthesis of PDMAEMA-PCL-PDMAEMA triblock copolymers

The synthesis of ABA triblock copolymers of the type PDMAEMA-PCL-PDMAEMA was achieved by atom transfer radical polymerization (ATRP) of DMAEMA using difunctional polycaprolactone (PCL) as macroinitiator. First, ring-opening polymerization (ROP) of ε-caprolactone (ε-CL) was carried out in the presence of 1,2-diaminoethane/tin (II) octanoate. Dihydroxy PCL thus obtained was end-functionalized in a quantitative manner using 2-bromoisobutyryl bromide. The resulting Br-PCL-Br was used as macroinitiator in the ATRP of DMAEMA leading to triblock copolymers with PCL as the central block and PDMAEMA sequences of different lengths. NMR and SEC analyses confirmed the formation of ABA triblocks.     

Controlled polymerizations of 2‐(dialkylamino)ethyl methacrylates and their block copolymers in protic solvents at ambient temperature via ATRP

Very well‐controlled polymerizations of 2‐(dimethylamino)ethyl methacrylate (DMAEMA) and 2‐(diethylamino)ethyl methacrylate (DEAEMA) in aqueous and methanolic solutions via atom transfer radical polymerization (ATRP) at ambient temperature were demonstrated. Poly(DMAEMA) and poly(DEAEMA) of low polydispersity index (PDI) of ～1.07 were obtained using the p‐toluenesulfonyl chloride/CuCl/1,1,4,7,10,10‐hexamethyl‐triethylenetetramine (p‐TsCl/CuCl/HMTETA) system. Excellent control of polymerization was achieved even in pure methanol. This is in contrast with the very poor control of DMAEMA ATRP in methanol reported previously using a different intiator/catalyst/ligand system. The initiator p‐TsCl underwent hydrolysis reaction in aqueous methanolic solutions with a second‐order rate constant of 6.1 × 10^?4 dm³ mol^?1 s^?1 at 25 °C. Both poly(DMAEMA) and poly(DEAEMA) retained almost full chlorine‐functionization at the chain ends. Well‐defined block copolymers of DEAEMA and DMAEMA were successfully obtained by starting with either macroinitiators of DEAEMA or DMAEMA. Other well‐defined diblock copolymers could be prepared using these macroinitiators. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5161–5169, 2004