Synthesis and UCST‐type phase behavior of OEGylated poly(γ‐benzyl‐l‐glutamate) in organic media

A series of OEGylated poly(γ‐benzyl‐l ‐glutamate) with different oligo‐ethylene‐glycol side‐chain length, molecular weight (MW = 8.4 × 10³ to 13.5 × 10⁴) and narrow molecular weight distribution (PDI = 1.12–1.19) can be readily prepared from triethylamine initiated ring‐opening polymerization of OEGylated γ‐benzyl‐l ‐glutamic acid based N‐carboxyanhydride. FTIR analysis revealed that the polymers adopted α‐helical conformation in the solid‐state. While they showed poor solubility in water, they exhibited a reversible upper critical solution temperature (UCST)‐type phase behavior in various alcoholic organic solvents (i.e., methanol, ethanol, 1‐propanol, 1‐butanol, 1‐pentanol, and isopropanol). Variable‐temperature UV–vis analysis revealed that the UCST‐type transition temperatures (T_pts) of the resulting polymers were highly dependent on the type of solvent, polymer concentration, side‐ and main‐chain length. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 1348‐1356     

Synthesis of a new 2‐amino‐glycan,poly‐(1→6)‐α‐D‐mannosamine,by ring‐opening polymerization of 1,6‐anhydro‐mannosamine derivatives

A stereoregular 2‐amino‐glycan composed of a mannosamine residue was prepared by ring‐opening polymerization of anhydro sugars. Two different monomers, 1,6‐anhydro‐2‐azido‐mannose derivative ( 3 ) and 1,6‐anhydro‐2‐(N, N‐dibenzylamino)‐mannose derivative ( 6 ), were synthesized and polymerized. Although 3 gave merely oligomers, 6 was promptly polymerized into high polymers of the number‐average molecular weight (M_n) of 2.3 × 10⁴ to 2.9 × 10⁴ with 1,6‐α stereoregularity. The differences of polymerizability of 3 and 6 from those of the corresponding glucose homologs were discussed. It was found that an N‐benzyl group is exceedingly suitable for protecting an amino group in the polymerization of anhydro sugars of a mannosamine type. The simultaneous removal of O‐ and N‐benzyl groups of the resulting polymers was achieved by using sodium in liquid ammonia to produce the first 2‐amino‐glycan, poly‐(1→6)‐α‐D ‐mannosamine, having high molecular weight through ring‐opening polymerization of anhydro sugars.© 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Synthesis of snowman‐like magnetic/nonmagnetic nanocomposite asymmetric particles via seeded emulsion polymerization initiated by γ‐ray radiation

We report on the synthesis of snowman‐like magnetic/nonmagnetic nanocomposite asymmetric particles (SMNAPs) via seeded emulsion polymerization initiated by γ‐ray radiation. In situ formation of magnetite in the presence of the emulsified poly(styrene‐divinylbenzene‐acrylic acid) microspheres affords raspberry‐like magnetic nanocomposite particles, which are used as seeds for further seeded emulsion polymerization induced by γ‐ray radiation. We study the effect of the kind of surfactant, the kind and content of second monomer, and the content of swelling agent on the morphologies of the final nanocomposite particles. It is found that SMNAPs can be fabricated in high yield using 12‐acryloxy‐9‐octadecenoic acid as the surfactant and styrene as the second monomer with the addition of 2‐butanone (a swelling agent). The as‐synthesized SMNAPs may serve as magnetically controllable solid surfactants to stabilize O/W immiscible mixtures, which preferentially orientated at the interface. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Arborescent polypeptides from γ‐benzyl l‐glutamic acid

The synthesis of arborescent polymers with poly(γ‐benzyl L‐glutamate) (PBG) side chains was achieved through successive grafting reactions. The linear PBG building blocks were produced by the ring‐opening polymerization of γ‐benzyl L‐glutamic acid N‐carboxyanhydride initiated with n‐hexylamine. The polymerization conditions were optimized to minimize the loss of amino chain termini in the reaction. Acidolysis of a fraction of the benzyl groups on a linear PBG substrate and coupling with linear PBG using a carbodiimide/hydroxybenzotriazole promoter system yielded a comb‐branched or generation zero (G0) arborescent PBG. Further partial deprotection and grafting cycles led to arborescent PBG of generations G1 to G3. The solvent used in the coupling reaction had a dramatic influence on the yield of graft polymers of generations G1 and above, dimethylsulfoxide being preferable to N,N‐dimethylformamide. This grafting onto scheme yielded well‐defined (M_w/M_n ≤ 1.06), high molecular weight arborescent PBG in a few reaction cycles, with number‐average molecular weights and branching functionalities reaching over 10⁶ and 290, respectively, for the G3 polymer. α‐Helix to coiled conformation transitions were observed from N,N‐dimethylformamide to dimethyl sulfoxide solutions, even for the highly branched polymers. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 5270–5279     

Synthesis,Characterization, and thermoresponsive properties of Helical Polypeptides Derivatized from Poly(γ−4‐(3‐chloropropoxycarbonyl)benzyl‐L‐glutamate)

A series of side‐chain‐functionalized α‐helical polypeptides, i.e., poly(γ‐4‐(3‐chloropropoxycarbonyl)benzyl‐_L‐glutamate) (6) have been prepared from n‐butylamine initiated ring‐opening polymerization (ROP) of γ‐4‐(3‐chloropropoxycarbonyl)benzyl‐_L‐glutamic acid‐based N‐carboxyanhydride. Polypeptides bearing oligo‐ethylene‐glycol (OEG) groups or 1‐butylimidazolium salts were prepared from 6 via copper‐mediated [2+3] alkyne‐azide 1,3‐dipolar cycloaddition or nuleophilic substitution, respectively. CD and FTIR analysis revealed that the polymers adopt α‐helical conformations both in solution and the solid state. Polymers bearing OEG (m = 3) side‐chains showed reversible LCST‐type phase transition behaviors in water while polymers bearing 1‐butylimidazolium and I^? counter‐anions exhibited reversible UCST‐type transitions in water. Variable‐temperature UV‐vis analysis revealed that the phase transition temperatures (T_pts) were dependent on the main‐chain length and polymeric concentration. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 2469–2480     

Cationic addition polymerization of 1,4‐dioxene using gacl3 as lewis acid catalyst: Long‐lived species‐mediated polymerization

Effective cationic addition polymerization of 1,4‐dioxene, a six‐membered cyclic olefin with two oxygen atoms adjacent to the double bond, was performed using a simple metal halide catalyst system in dichloromethane. The polymerization was controlled when the reaction was conducted using GaCl₃ in conjunction with an isobutyl vinyl ether–HCl adduct as a cationogen at –78°C to give polymers with predetermined molecular weights and relatively narrow molecular weight distributions. The long‐lived properties of the propagating species were further confirmed by a monomer addition experiment and the analyses of the product polymers by ¹H NMR and MALDI–TOF–MS. Although highly clean propagation proceeded, the apparent rate constant changed during the controlled cationic polymerization of 1,4‐dioxene. The reason for the change was discussed based on polymerization results under various conditions. The obtained poly(1,4‐dioxene) exhibited a very high glass transition temperature (T_g) of 217°C and unique solubility. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Scalable ambient synthesis of water‐soluble poly(β‐hydroxythio‐ether)s

Proton transfer polymerization through thiol‐epoxy “click” reaction between commercially available and hydrophilic di‐thiol and di‐epoxide monomers is carried out under ambient conditions to furnish water‐soluble polymers. The hydrophilicity of monomers permitted use of aqueous tetrahydrofuran as the reaction medium. A high polarity of this solvent system in turn allowed for using a mild catalyst such as triethylamine for a successful polymerization process. The overall simplicity of the system translated into a simple mixing of monomers and isolation of the reactive polymers in an effortless manner and on any scale required. The structure of the resulting polymers and the extent of di‐sulfide defects are studied with the help of 13C‐ and ¹H‐NMR spectroscopy. Finally, reactivity of the synthesized polymers is examined through post‐polymerization modification reaction at the backbone sulfur atoms through oxidation reaction. The practicality, modularity, further functionalizability, and water solubility aspects of the described family of new poly(β‐hydroxythio‐ether)s is anticipated to accelerate investigations into their potential utility in bio‐relevant applications. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 3381–3386     

Controlled/living free‐radical copolymerization of 4‐(azidocarbonyl) phenyl methacrylate with methyl acrylate under 60Co γ‐ray irradiation

A new vinyl acyl azide monomer, 4‐(azidocarbonyl) phenyl methacrylate, has been synthesized and characterized by NMR and FTIR spectroscopy. The thermal stability of the new monomer has been investigated with FTIR and thermal gravimetry/differential thermal analysis (TG/DTA), and the monomer has been demonstrated to be stable below 50 °C in the solid state. The copolymerizations of the new monomer with methyl acrylate have been carried out at room temperature under ⁶⁰Co γ‐ray irradiation in the presence of benzyl 1H‐imidazole‐1‐carbodithioate. The results show that the polymerizations bear all the characteristics of controlled/living free‐radical polymerizations, such as the molecular weight increasing linearly with the monomer conversion, the molecular weight distribution being narrow (<1.20), and a linear relationship existing between ln([M]₀/[M]) and the polymerization time. The data from ¹H NMR and FTIR confirm that no change in the acyl azide groups has occurred in the polymerization process and that acyl azide copolymers have been obtained. The thermal stability of the polymers has also been investigated with TG/DTA and FTIR. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 2609–2616, 2007     

Investigation of catalyst‐transfer condensation polymerization for the synthesis of n‐type π‐conjugated polymer,poly(2‐dioxaalkylpyridine‐3,6‐diyl)

Kumada‐Tamao coupling polymerization of 6‐bromo‐3‐chloromagnesio‐2‐(3‐(2‐methoxyethoxy)propyl)pyridine 1 with a Ni catalyst and Suzuki‐Miyaura coupling polymerization of boronic ester monomer 2 , which has the same substituted pyridine structure, with ^tBu₃PPd(o‐tolyl)Br were investigated for the synthesis of a well‐defined n‐type π‐conjugated polymer. We first carried out a model reaction of 2,5‐dibromopyridine with 0.5 equivalent of phenylmagnesium chloride in the presence of Ni(dppp)Cl₂ and then observed exclusive formation of 2,5‐diphenylpyridine, indicating that successive coupling reaction took place via intramolecular transfer of Ni(0) catalyst on the pyridine ring. Then, we examined the Kumada‐Tamao polymerization of 1 and found that it proceeded homogeneously to afford soluble, regioregular head‐to‐tail poly(pyridine‐2,5‐diyl), poly(3‐(2‐(2‐(methoxyethoxy)propyl)pyridine) (PMEPPy). However, the molecular weight distribution of the polymers obtained with several Ni and Pd catalysts was very broad, and the matrix‐assisted laser desorption ionization time‐of‐flight mass spectra showed that the polymer had Br/Br and Br/H end groups, implying that the catalyst‐transfer polymerization is accompanied with disproportionation. Suzuki‐Miyaura polymerization of 2 with ^tBu₃PPd(o‐tolyl)Br also afforded PMEPPy with a broad molecular weight distribution, and the tolyl/tolyl‐ended polymer was a major product, again indicating the occurrence of disproportionation. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Magnesium complexes incorporated by sulfonate phenoxide ligands as efficient catalysts for ring‐opening polymerization of ε‐caprolactone and trimethylene carbonate

Two novel sulfonate phenol ligands—3,3′‐di‐tert‐butyl‐2′‐hydroxy‐5,5′,6,6′‐tetramethyl‐biphenyl‐2‐yl 4‐X‐benzenesulfonate (X?CF₃, L^CF3 ‐H, and X?OCH₃, L^OMe ‐H)—were prepared through the sulfonylation of 3,3′‐di‐tert‐butyl‐5,5′,6,6′‐tetramethylbiphenyl‐2,2′‐diol with the corresponding 4‐substituted benzenesulfonyl chloride (1 equiv.) in the presence of excess triethylamine. Magnesium (Mg) complexes supported by sulfonate phenoxide ligands were synthesized and characterized structurally. The reaction of MgⁿBu₂ with L‐H (2 equiv.) produces the four‐coordinated monomeric complexes ( L^CF3 )₂Mg ( 1 ) and ( L^OMe )₂Mg ( 2 ). Complexes 1 and 2 are efficient catalysts for the ring‐opening polymerization of ε‐caprolactone (ε‐CL) and trimethylene carbonate (TMC) in the presence of 9‐anthracenemethanol; complex 1 catalyzes the polymerization of ε‐CL and TMC in a controlled manner, yielding polymers with the expected molecular weights and narrow polydispersity indices (PDIs). In ε‐CL polymerization, the activity of complex 1 is greater than that of complex 2 , likely because of the greater Lewis acidity of Mg²⁺ metal caused by the electron‐withdrawing substitute trifluoromethyl (? CF₃) at the 4‐position of the benzenesulfonate group. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3564–3572, 2010     

Syntheses of trimethoxysilyl‐endcapped polylactones via 3‐mercaptopropyl trimethoxysilane

Monofunctional polylactones were prepared by Bu₂Sn(OMe)₂‐initiated ring‐opening polymerization of ε‐caprolactone (εCL) followed by acylation with bromoacetylbromide. Telechelic polylactones and polylactides were prepared via ring‐expansion polymerization with 2,2‐dibutyl‐2‐stanna‐1,3‐dioxepane (DSDOP) or 2,2‐dibutyl‐2‐stanna‐pentaoxacyclotridecane (Bu₂SnTEG) as cyclic initiator. In situ combination of the polymerization with condensation by means of bromoacetylbromide yielded polylactones having bromoacetate endgroups. These endgroups were subjected to nucleophilic substitution with 3‐mercaptopropyl trimethoxysilane (3‐MPTMS). Analogous experiments were conducted with dl‐lactide. The telechelic trimethoxysilyl‐endcapped polylactones were characterized by viscosity, ¹H and ¹³C NMR‐spectroscopy, and MALDI‐TOF mass spectrometry. The mass spectra revealed small amounts of cyclic oligolactones as byproducts in all samples. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3667–3674, 2005     

Synthesis and properties of star polymers with a C5‐symmetric bowl‐shaped aromatic core

We report the synthesis and properties of star polymers with a C₅‐symmetric aromatic core. For this, corannulene‐based penta‐substituted polymerization initiators were synthesized. These initiators were then used to polymerize cyclic ester and styrenic monomers via ring opening polymerization and free radical polymerization methods, respectively. Preliminary results suggest that these novel polymers can interact with fullerene, C₆₀, and the degree of interaction can be tuned by the chemical nature of the solvent. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

In situ formation of Sn(IV) catalyst with increased activity in ε‐caprolactone and L‐lactide polymerization using stannous(II) 2‐ethylhexanoate

Ring‐opening polymerization (ROP) of ε‐caprolactone and L‐lactide (LA) was studied using stannous(II) 2‐ethylhexanoate (Sn(Oct)₂) with N,N‐dimethylformamide‐dimethyl acetal (DMF‐DMA). DMF‐DMA showed a tenfold improvement in catalytic activity over that of Sn(Oct)₂ under the same conditions. It also enhanced the capability to control molecular weight in the synthesis of small molecular weight polymers of polycaprolactone and polylactide (PLA). The high molecular weight polymerization demonstrated a strong capability to control molecular weight for the polymerization of LA: a molecular weight of PLA exceeding 400,000 was obtained at very low catalytic loadings. The individual polymerization rates of other tin reagents with DMF‐DMA also clearly increased. Applying this methodology could drastically reduce the time and cost required for the fabrication of these products to increase the competitive advantage of manufacturers. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

ATRP of MMA under 60Co γ‐irradiation at room temperature

In this work, atom transfer radical polymerization (ATRP) of methyl methacrylate (MMA) was successfully carried out at room temperature (25 °C) under ⁶⁰Co γ‐irradiation environment. The polymerization proceeded smoothly with high conversion (>90%) within 7 h. The polymerizations kept the features of controlled radical polymerization: first‐order kinetics, well‐predetermined number‐average molecular weights (M_n,GPC), and narrow molecular weight distributions (M_w/M_n < 1.25). ¹H NMR spectroscope and matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry confirmed that poly(methyl methacrylate) (PMMA) chain was end‐capped by the initiator moieties. The Cu(II) concentration could reduce to 20 ppm level while keeping good control over molecular weights. This is the first successful example for the ATRP of MMA under ⁶⁰Co γ‐irradiation at room temperature. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Kinetic study of copper(I)‐catalyzed click chemistry step‐growth polymerization

Oligomers and polymers containing triazole units were synthesized by the copper(I)‐catalyzed 1,3‐dipolar cycloaddition step‐growth polymerization of four difunctional azides and alkynes. In a first part, monofunctional benzyl azide was used as a chain terminator for the polyaddition of 1,6‐diazidohexane and α,ω‐bis(O‐propargyl)diethylene glycol, leading to polytriazole oligomers of controlled average degree of polymerization (DP_n = 3–20), to perform kinetic studies on low‐viscosity compounds. The monitoring of the step‐growth click polymerization by ¹H NMR at 25, 45, and 60 °C allowed the determination of the activation energy of this click chemistry promoted polyaddition process, that is, E_a = 45 ± 5 kJ/mol. The influence of the catalyst content (0.1–5 mol % of Cu(PPh₃)₃Br according to azide or alkyne functionalities) was also examined for polymerization kinetics performed at 60 °C. In a second part, four high molar mass polytriazoles were synthesized from stoichiometric combinations of diazide and dialkyne monomers above with p‐xylylene diazide and α,ω‐bis(O‐propargyl)bisphenol A. The resulting polymers were characterized by DSC, TGA, SEC, and ¹H NMR. Solubility and thermal properties of the resulting polytriazoles were discussed based on the monomers chemical structure and thermal analyses. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5506–5517, 2008     

Stereoregular control of poly(4‐vinyl pyridine) on free radical polymerization by using the inclusion complex with randomly methylated β‐cyclodextrin

Highly heterotactic poly(4‐vinyl pyridine)s (P4VPs) with the fraction of mr content (f_mr) > 0.81 were synthesized by free radical polymerization of 4‐vinyl pyridine (4VP) with randomly methylated β‐cyclodextrin (β‐RMCD) in acidic aqueous media of HNO₃ and CF₃COOH at 40 °C. The heterotacticity of P4VP strongly depended on the neutralization of 4VP. The complete neutralization of 4VP with HNO₃ or CF₃COOH increased the heterotacticity of P4VP, whereas atactic P4VP was obtained in water. The partial decomposition of β‐RMCD by HCl reduced the heterotacticity of P4VP (f_mr ≈ 0.74). The structures of inclusion complexed monomers were determined by Job's plot, 2D NMR with nuclear Overhauser enhancement spectroscopy analyses, and simulation by MM2. The 1:2 complex with [β‐RMCD]:[4VP] with meso placement of 4VPs in β‐RMCD was formed when 4VP was completely neutralized with acid, whereas the 1:1 complex was formed in water. The mechanism of heterospecific control by using β‐RMCD was proposed. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

One‐pot inimer promoted ROCP synthesis of branched copolyesters using α‐hydroxy‐γ‐butyrolactone as the branching reagent

An array of branched poly(?‐caprolactone)s was successfully synthesized using an one‐pot inimer promoted ring‐opening multibranching copolymerization (ROCP) reaction. The biorenewable, commercially available yet unexploited comonomer and initiator 2‐hydroxy‐γ‐butyrolactone was chosen as the inimer to extend the use of 5‐membered lactones to branched structures and simultaneously avoiding the typical tedious work involved in the inimer preparation. Reactions were carried out both in bulk and in solution using stannous octoate (Sn(Oct)₂) as the catalyst. Polymerizations with inimer equivalents varying from 0.01 to 0.2 were conducted which resulted in polymers with a degree of branching ranging from 0.049 to 0.124. Detailed ROCP kinetics of different inimer systems were compared to illustrate the branch formation mechanism. The resulting polymer structures were confirmed by ¹H, ¹³C, and ₁H‐₁₃C HSQC NMR and SEC (RI detector and triple detectors). The thermal properties of polymers with different degree of branching were investigated by DSC, confirming the branch formation. Through this work, we have extended the current use of the non‐homopolymerizable γ‐butyrolactone to the branched polymers and thoroughly examined its behaviors in ROCP. © 2016 The Authors. Journal of Polymer Science Part A: Polymer Chemistry Published by Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 1908–1918     

Living regioselective copolymerization of ethylene with nonconjugated bicyclic dienes using (salicylaldiminato)(β‐enaminoketonato) titanium catalysts

A series of heteroligated (salicylaldiminato)(β‐enaminoketonato)titanium complexes [3‐^tBu‐2‐OC₆H₃CH?N(C₆F₅)] [PhN?C(CF₃)CHCRO]TiCl₂ [ 3a : R = Ph, 3b : R = C₆H₄Cl(p), 3c : R = C₆H₄OMe(p), 3d : R = C₆H₄Me(p), 3e : R = C₆H₄Me(o)] were synthesized and characterized. Molecular structures of 3b and 3c were further confirmed by X‐ray crystallographic analyses. In the presence of modified methylaluminoxane as a cocatalyst, these unsymmetric catalysts displayed favorable ability to incorporate 5‐vinyl‐2‐norbornene (VNB) and 5‐ethylidene‐2‐norbornene (ENB) into the polymer chains, affording high‐molecular weight copolymers with high‐comonomer incorporations and alternating sequence under the mild conditions. The comonomer concentration in the polymerization medium had a profound influence on the molecular weight distribution of the resultant copolymer. At initial comonomer concentration of higher than 0.4 mol/L, the titanium complexes with electron‐donating groups in the β‐enaminoketonato moiety mediated room‐temperature living ethylene/VNB or ENB copolymerizations. Polymerization results coupled with density functional theory calculations suggested that the highly controlled living copolymerization is probably a consequence of the difficulty in chain transfer of VNB (or ENB)‐last‐inserted species and some characteristics of living ethylene polymerization under limited conditions. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Synthesis of well‐defined photoresist materials by SET‐LRP

Single electron transfer‐living radical polymerization (SET‐LRP) provides an excellent tool for the straightforward synthesis of well‐defined macromolecules. Heterogeneous Cu(0)‐ catalysis is employed to synthesize a novel photoresist material with high control over the molecular architecture. Poly(γ‐butyrolactone methacrylate)‐co‐(methyladamantly methacrylate) was synthesized. Kinetic experiments were conducted demonstrating that both monomers, γ‐butyrolactone methacrylate (GBLMA) and methyl adamantly methacrylate (MAMA), are successfully homopolymerized. In both cases polymerization kinetic is of first order and the molecular weights increase linearly with conversion. The choice of a proper solvent was decisive for the SET‐LRP process and organic solvent mixtures were found to be most suitable. Also, the kinetic of the copolymerization of GBLMA and MAMA was investigated. Following first order kinetics in overall monomer consumption and exhibiting a linear relationship between molecular weights and conversion a “living” process was established. This allowed for the straightforward synthesis of well‐defined photoresist polymers. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2251–2255, 2010     

Association of hydrophobically α,ω‐end‐capped poly(2‐methyl‐2‐oxazoline) in water

The α,ω‐end‐capped poly(2‐methyl‐2‐oxazoline) (C_n‐POXZ‐C_n) have been synthesized by a one‐pot process using cationic ring‐opening polymerization with an appropriate initiator and terminating agent. The polymers bearing different alkyl groups C₁₂ and C₁₈ have molecular weight in the range of 2.4 × 10³ to 14 × 10³ with a small polydispersity index. The solution behavior of the free chains has been analyzed in a nonselective solvent, dichloromethane, by small‐angle neutron scattering and dynamic light scattering. These amphiphilic polymers associate in water to form flower‐like micellar structures. Critical micelle concentrations, investigated by fluorescence technique, are in the range of 0.03–0.5 g L^?1 and are dependent on the hydrophilic/lipophilic balance. The structural properties of the aggregates have also been investigated by viscometry. Intrinsic viscosities of these polymers are in the same range as that of the precursors poly(2‐methyl‐2‐oxazoline) (POXZ) and mono‐functionalized polymers. Large viscosity increase corresponding to intermicellar bridging was observed in the vicinity of the micelle overlap concentration. Addition of hydroxypropyl β‐cyclodextrin (HβCD) has dissociated the aggregates and the intrinsic viscosities of the HβCD‐end‐capped chains have become comparable with the ones of POXZ precursor chains. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2477–2485, 2010