Anionic homo‐ and copolymerization of styrenic triple‐tailed polybutadiene macromonomers

A number of well‐defined complex macromolecular architectures have been synthesized using an efficient macromonomer technique. Styrenic triple‐tailed polybutadiene (PBd) macromonomers (sTMMB), synthesized by selective reaction (titration) of living PBd tails with the SiCl groups of 2‐(dichloromethylsilyl)ethylchloromethylsilyl‐4‐styrene (TCDSS), were polymerized in situ without isolation of sTMMB with s‐BuLi, using high vacuum techniques. Taking advantage of the living character of the anionic polymerization of sTMMB, the following complex macromolecular architectures were prepared: PBd‐g‐(PBd)₃ (triple‐combs), PS‐g‐(PBd)₃ (triple‐grafts), [PBd‐g‐(PBd)₃]₃ (3‐arm triple‐comb stars), and triple molecular brushes (tmbPBd) or triple polymacromonomers (tPMMB). Characterization carried out by size exclusion chromatography (SEC), equipped with refractive index and light scattering detectors, indicated that the synthesized novel architectures have a high degree of molecular and compositional homogeneity. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3513–3523, 2007     

Well‐defined complex macromolecular architectures by anionic polymerization of styrenic single and double homo/miktoarm star‐tailed macromonomers

Styrenic single and double star‐tailed macromonomers were synthesized by selective reaction of living homo/miktoarm stars with the chlorosilane groups of 4‐(chlorodimethylsilyl)‐ and 4‐(dichloromethylsilyl)styrene, respectively. The in situ anionic homopolymerization of macromonomers with sec‐BuLi and copolymerization with butadiene and styrene, led to single/double homo/miktoarm star‐tailed molecular brushes and combs, as well as a block copolymer consisting of a linear polystyrene chain and a double miktoarm (PBd/PS) star‐tailed brush‐like block. Molecular characterization by size exclusion chromatography, size exclusion chromatography/two‐angle laser light scattering, and NMR spectroscopy, revealed the high molecular/compositional homogeneity of all intermediate and final products. These are only a few examples of the plethora of complex architectures possible using the above macromonomers. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 1826–1842, 2008     

Anionic copolymerization of styrenic‐tipped macromonomers: A route to novel triblock–comb copolymers of styrene and isoprene

The following triblock–comb copolymers of isoprene (I) and styrene (S)—PS‐b‐(PI‐g‐PI)‐b‐PS, PS‐b‐[PI‐g‐(PI‐b‐PS)]‐b‐PS, and (PS‐g‐PS)‐b‐(PI‐g‐PI)‐b‐(PS‐g‐PS) (where PS is polystyrene and PI is polyisoprene)—with PS contents of 20–30% were synthesized with high‐vacuum techniques and the anionic copolymerization of styrenic‐tipped macromonomers with I and S. The macromonomers, prepared by the reaction of living PI or PS with 4‐(chlorodimethylsilyl) styrene, were used without isolation. Molecular characterization by size exclusion chromatography, size exclusion chromatography/two‐angle laser light scattering, and NMR spectroscopy indicated that the triblock–comb copolymers had high molecular and compositional homogeneity. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4030–4039, 2005     

Titanium‐mediated [CpTiCl2(OEt)] ring‐opening polymerization of lactides: A novel route to well‐defined polylactide‐based complex macromolecular architectures

Among three cyclopentadienyl titanium complexes studied, CpTiCl₂(OEt), containing a 5% excess CpTiCl₃, has proven to be a very efficient catalyst for the ring‐opening polymerization (ROP) of L ‐lactide (LLA) in toluene at 130 °C. Kinetic studies revealed that the polymerization yield (up to 100%) and the molecular weight increase linearly with time, leading to well‐defined PLLA with narrow molecular weight distributions (M_w/M_n ≤ 1.1). Based on the above results, PS‐b‐PLLA, PI‐b‐PLLA, PEO‐b‐PLLA block copolymers, and a PS‐b‐PI‐b‐PLLA triblock terpolymer were synthesized. The synthetic strategy involved: (a) the preparation of OH‐end‐functionalized homopolymers or diblock copolymers by anionic polymerization, (b) the reaction of the OH‐functionalized polymers with CpTiCl₃ to give the corresponding Ti‐macrocatalyst, and (c) the ROP of LLA to afford the final block copolymers. PMMA‐g‐PLLA [PMMA: poly(methyl methacrylate)] was also synthesized by: (a) the reaction of CpTiCl₃ with 2‐hydroxy ethyl methacrylate, HEMA, to give the Ti‐HEMA‐catalyst, (b) the ROP of LLA to afford a PLLA methacrylic‐macromonomer, and (c) the copolymerization (conventional and ATRP) of the macromonomer with MMA to afford the final graft copolymer. Intermediate and final products were characterized by NMR spectroscopy and size exclusion chromatography, equipped with refractive index and two‐angle laser light scattering detectors. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1092–1103, 2010     

Anionic polymerization of n‐hexyl isocyanate with monofuctional initiators. Synthesis of well‐defined diblock copolymers with styrene and isoprene

Several monofunctional initiators, such as s‐BuLi, 1,1‐diphenyl‐4‐methylpentyl lithium (DPMPL), benzyl potassium (BzK), triphenylmethyl sodium (trityl sodium, TrNa) and benzyl sodium (BzNa) were tested and evaluated for the polymerization of n‐hexyl isocyanate (HIC) in THF at ?98 °C. The polymerizations were conducted either without or with additives, such as LiBPh₄, NaBPh₄, and crown ether 18C6. The products were characterized by size exclusion chromatography (SEC), membrane osmometry (MO), and ¹H NMR spectroscopy. The best results regarding polymerization yield, molecular weight distribution, and agreement between the stoichiometric and the experimentally observed molecular weight were obtained by the initiating system BzNa/NaBPh₄ in a molar ratio 1/10. By using BzNa/NaBPh₄ system, well‐defined block copolymers of HIC with styrene or isoprene were synthesized for the first time. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3533–3542, 2005     

Oxazoline‐terminated macromonomers by the alkylation of 2‐methyl‐2‐oxazoline

Well‐defined macromonomers of poly(ethylene oxide) and poly(tert‐butyl methacrylate) were obtained by anionic polymerization induced directly by the carbanion issued from 2‐methyl‐2‐oxazoline. When ethylene oxide was added to this carbanion with lithium as the counterion, a new compound able to initiate the polymerization of ε‐caprolactone in an anionically coordinated way was synthesized, and this led to well‐defined poly(ε‐caprolactone) macromonomers. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2440–2447, 2005     

Anionic polymerization of styrenic macromonomers of polyisoprene,polybutadiene, and polystyrene

Anionic polymerization and high‐vacuum techniques were used to prepare a series of well‐defined polyisoprene, polybutadiene, and polystyrene polymacromonomers. The procedure involved (1) the synthesis of styrenic macromonomers in benzene by the selective reaction of the corresponding macroanion with the chlorine of 4‐(chlorodimethylsilyl)styrene (CDMSS) and (2) the in situ anionic polymerization of the macromonomer without previous isolation. The synthesis of the macromonomers [polyisoprene macromonomer: 11 samples, weight‐average molecular weight (M_w) = 1000–18,000; polybutadiene macromonomer: 5 samples, M_w = 2000–4000; and polystyrene macromonomer: 2 samples, M_w = 1300 and 3600] was monitored by size exclusion chromatography with refractive index/ultraviolet detectors. Selectivity studies with CDMSS indicated that polybutadienyllithum had the highest selectivity, and polystryryllithium the lowest. From kinetic studies it was concluded that the polymerization half‐life times were longer but comparable to those of styrene, and they appeared to only slightly depend on the molecular weight of the macromonomer chain (at least for low degrees of polymerization of the polymacromonomer and for M_w < 7000 for the macromonomer side chain). Dependence on the polymerization degree of the polymacromonomer product was also observed. All the prepared polymacromonomers were characterized by size exclusion chromatography with refractive index, ultraviolet and two‐angle laser light scattering detectors, and NMR spectroscopy. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1038–1048, 2005     

Pulsed‐laser polymerization‐gel permeation chromatographic determination of the propagation‐rate coefficient for the methyl acrylate dimer: A sterically hindered monomer

The methyl acrylate dimer (MAD) is a sterically hindered macromonomer, and the propagating radical can fragment to an unsaturated end group. The propagation‐rate coefficient (k_p) for MAD was obtained by pulsed‐laser polymerization (PLP). The Mark–Houwink–Sakaruda parameters required for the analysis of the molecular weight distributions (MWDs) were obtained by multiple‐detector gel permeation chromatography (GPC) with on‐line viscometry. The small radical created by the fragmentation results in a short‐chain polymer that means the MWD may no longer be given by that expected for “ideal” PLP conditions; simulations suggest that the degree of polymerization required for “ideal” PLP conditions can be obtained from the primary point of inflection provided the GPC traces also show a clear secondary inflection point (radicals terminated by the second, rather than the first, pulse subsequent to initiation). Over the temperature range of 40–75 °C, the data can be best fitted by k_p/dm³ mol^?1 s^?1 = 10^6.1 exp(?29.5 kJ mol^?1), with a moderately large joint confidence interval for the Arrhenius parameters. The data are consistent with an increased activation energy and reduced frequency factor as compared with acrylate or methacrylate; both of these changes can be ascribed to hindrance. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3902–3915, 2001     

Controlled ring‐opening homo‐ and copolymerization of ɛ‐caprolactone and d,l‐lactide by iminophenolate aluminum complexes: An efficient approach toward well‐defined macromonomers

The aluminum complexes containing two iminophenolate ligands of the type (p‐XC₆H₄NCHC₆H₄O‐o)₂AlR' (R′=Me ( 3, 4 ) or R′=O(CH₂)₄OCH=CH₂ ( 5, 6 ), X=H ( 3, 5 ), F( 4, 6 )) were synthesized and characterized by ¹H, ¹³C NMR spectroscopy, and X‐ray crystallography. The reaction of AlMe₃ with two equivalents of substituted iminophenols gave five‐coordinated {ONR}₂AlMe ( 3, 4 ) complexes. Subsequent reaction of these methyl complexes with unsaturated alcohol, HO(CH₂)₄OCH=CH₂, resulted in target compounds 5 and 6 in a good yield. It was shown that the complexes ( 3 ‐ 6 ) are monomeric in solution (NMR) and in solid state (X‐ray analysis). The catalytic activity of the complexes 5 and 6 towards ring‐opening polymerization (ROP) of ?‐caprolactone and d,l ‐lactide was assessed. Complex 5 showed higher activity as compared with 6 , while both of these catalysts induced controlled homo‐ and copolymerization to afford the macromonomers with high content of vinyl ether end groups (F_n > 80%) in a broad range of molecular weights (M_n = 4000–30,000 g mol^?1) with relatively narrow MWD (M_w/M_n = 1.1–1.5). © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 1237–1250     

Polymerization and self‐assembly of thermally responsive in‐chain functionalized double‐hydrophilic macromonomers

Double‐hydrophilic in‐chain functionalized macromonomers consisting of poly(N‐isopropylacrylamide) (PNIPAM) and poly(ethylene oxide) were prepared by a multistep procedure including esterification of PNIPAM monoester of maleic acid with α‐methoxy‐ω‐hydroxypolyoxyethylene or its amidation with α‐methoxy‐ω‐aminopolyoxyethylene. The polymerization of the macromonomers was carried out in aqueous solutions. The temperature was the key parameter controlling the polymerization process that was performed in the organized domains formed by the macromonomers below and above the phase transition temperature (T_tr). Polymacromonomers with higher degrees of polymerization were prepared at temperatures just below the T_tr. Static light scattering measurements on dilute aqueous solutions of thermally‐responsive macromonomers and their polymerization products demonstrated that they formed aggregates below the T_tr. Supramolecular structures with low density cores, formed by the polymacromonomers at room temperature, were imaged by SEM. Morphological tuning was achieved by varying both the composition of the copolymer and the concentration of the aqueous solution. The rheological behavior of the polymacromonomers in 25 wt % aqueous solution was compared to that of the respective macromonomers. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4720–4732, 2007     

Anionic alternating copolymerization of epoxide and six‐membered lactone bearing naphthyl moiety

This article describes the anionic copolymerization of glycidyl phenyl ether (GPE) and 1,2‐dihydro‐3H‐naphtho[2,1‐b]pyran‐3‐one (DHNP), a six‐membered aromatic lactone bearing naphthyl moiety. The copolymerization proceeded in a 1:1 alternating manner, to afford the corresponding polyester. The ester linkage in the main chain was cleavable by reduction with lithium aluminum hydride to give the corresponding diol that inherited the structure of the alternating sequence. The copolymerization ability of DHNP permitted its addition as a comonomer to an imidazole‐initiated polymerization of bisphenol A diglycidyl ether. The resulting networked polymer, of which main chain was endowed with the DHNP‐derived rigid naphthalene moieties, showed a higher glass transition temperature than that obtained similarly with using 3,4‐dihydrocoumarin (DHCM) as a comonomer, an analogous aromatic lactone bearing phenylene moiety instead of naphthalene moiety of DHNP. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

On the anionic homo‐ and copolymerization of ethyl‐ and butyl‐2‐cyanoacrylates

Ethyl‐(ECA) and butyl‐2‐cyanoacrylate (BCA) monomers of high purity and acidic stabilization were synthesized and anionically polymerized to homo‐ and copolymers in two different ways: by piperidine‐catalyzed bulk polymerization leading to transparent, brittle films (method A) and by polymerization in aqueous medium in the presence of sodium bicarbonate to obtain white powders (Method B). The molecular structure of the synthesized monomers, homopolymers and copolymers were corroborated by spectral methods. The polymers were studied further by thermal gravimetric analysis (TGA), differential scanning calorimetry (DSC), size exclusion chromatography (SEC) and proton nuclear magnetic resonance (¹H NMR). Controlling the composition of the monomer feed and the way the polymerization was performed, it was possible to obtain phase separated or homogeneous cyanoacrylate copolymers with glass transitions varying between the T_g of polyECA and that of polyBCA. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5142–5156, 2008     

Synthesis and Self-Assembly of 2nd Generation Dendritic Homopolymers and Copolymers of Polydienes with Different Isomeric Microstructures

Synthesis of 2^nd generation dendritic polymeric materials via anionic polymerization procedures in combination with chlorosilane chemistry, consisting either from one polydienic segment (homopolymers) or from two chemically different polydienic components (copolymers), is described. The polydienes used were poly(butadiene) (PB) with ∼90% 1,4-isomerism and poly(isoprene) (PI) with increased 3,4-isomerism (∼60%). Molecular characterization of intermediate products and the final dendritic materials was made with Gel Permeation Chromatography (GPC), Membrane and Vapour Pressure Osmometry (MO and VPO respectively), Gas Chromatography –Mass Spectroscopy (GC-MS) and ¹H-Nuclear Magnetic Resonance (¹H-NMR) Spectroscopy, leading to the conclusion that they can be considered model polymers. Morphological studies solely with Transmission Electron Microscopy (TEM) have been conducted on two of the four synthesized copolymer samples exhibiting microphase separation between the two polydiene segments.     

Synthesis via ATRP,kinetics study and characterization (molecular‐morphological) of 3‐Arm star diblock copolymers of the (PS‐b‐P2VP)3 type

The synthesis of five homopolymers (PS)₃ and the corresponding diblock copolymer 3‐arm stars of the (PS‐b‐P2VP)₃ type is reported through atom transfer radical polymerization. Such star homo‐ and copolymers are prepared without any addition of solvent (bulk polymerization). The kinetics study results lead to the ability of predicting the best polymerization time with high values of monomer to polymer conversion, sufficient polydispersity indices and average molecular weights. Molecular characterization through size exclusion chromatography, viscometry, low‐angle laser light scattering, proton and carbon nuclear magnetic resonance spectroscopy (¹H NMR and ¹³C NMR, respectively) verified the successful synthesis of both homopolymer and copolymer 3‐arm star‐like architectures. Furthermore, the morphological characterization of the final copolymers is reported through transmission electron microscopy studies verifying the self‐assembly without any indication of homopolymer or Cu(I) traces. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 23–32     

Functionalization of polymeric organolithium compounds with 3,4‐epoxy‐1‐butene: Precursors for diene‐functionalized macromonomers

The functionalization of polymeric organolithiums (PLi) with 3,4‐epoxy‐1‐butene (EPB) in a hydrocarbon solution yielded the corresponding hydroxybutene‐functionalized polymers in high yields (>95%). Three modes of addition of PLi to EPB were observed (1,4, 3,4, and 4,3). The products and chain‐end structures were characterized by ¹H NMR, ¹³C NMR, attached‐proton‐test ¹³C NMR, calculated ¹³C NMR chemical shifts, and matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry (MALDI‐TOF MS). The regioselectivity of the addition depended on the PLi chain‐end structure, the reaction conditions, and the addition of lithium salts or Lewis bases. In the absence of additives, the functionalization of poly(styryl)lithium (PSli) produced equal amounts of 1,4‐, 3,4‐, and 4,3‐addition, as determined by quantitative ¹³C NMR analysis. The use of a low temperature (6 °C), inverse addition, the addition of triethylamine (TEA; [TEA]/[PSLi] = 20) as a Lewis base, or dienyllithium chain ends produced polymers with only the 1,4‐addition product. Mild dehydration of the hydroxybutene‐functionalized polymer with p‐toluenesulfonic acid produced the corresponding diene‐functionalized macromonomer, as shown by MALDI‐TOF MS. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 947–957, 2003     

Dendrimer‐like miktoarm star terpolymers: A3‐(B‐C)3 via click reaction strategy

Two samples of dendrimer‐like miktoarm star terpolymers: (poly(tert‐butyl acrylate))₃‐(polystyrene‐poly(ε‐caprolactone))₃ (PtBA)₃‐(PS‐PCL)₃, and (PS)₃‐(PtBA‐poly(ethylene glycol)₃ were prepared using efficient Cu catalyzed Huisgen cycloaddition (click reaction). As a first step, azido‐terminated 3‐arm star polymers PtBA and PS as core (A) were synthesized by atom transfer radical polymerization (ATRP) of tBA and St, respectively, followed by the conversion of bromide end group to azide. Secondly, PS‐PCL and PtBA‐PEG block copolymers with alkyne group at the junction as peripheral arms (B‐C) were obtained via multiple living polymerization mechanisms such as nitroxide mediated radical polymerization (NMP) of St, ring opening polymerization (ROP) of ε‐CL, ATRP of tBA. Thus obtained core and peripheral arms were linked via click reaction to give target (A)₃‐(B‐C)₃ dendrimer‐like miktoarm star terpolymers. (PtBA)₃‐(PS‐PCL)₃ and (PS)₃‐(PEG‐PtBA)₃ have been characterized by GPC, DSC, AFM, and SAXS measurements. (PtBA)₃‐(PS‐PCL)₃ did not show any self‐organization with annealing due to the miscibility of the peripheral arm segments. In contrast, the micro‐phase separation of the peripheral arm segments in (PS)₃‐(PtBA‐PEG)₃ resulted in self‐organized phase‐separated morphology with a long period of ～ 13 nm. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5916–5928, 2008     

Anionic synthesis and detection of fluorescence‐labeled polymers with a terminal anhydride group

To monitor polymer–polymer coupling reactions between two different monofunctional polymers in dilute polymer blends, fluorescence‐labeled anhydride‐functional polystyrene (PS) and poly(methyl methacrylate) (PMMA) were prepared by conventional anionic polymerization. Sequential trapping of lithiopolystyrene by 1‐(2‐anthryl)‐1‐phenylethylene (APE) and then di‐t‐butyl maleate (4) provided, after pyrolysis, anhydride‐functional fluorescent PS. Fluorescent PMMA anhydride (8) was synthesized with sec‐butyllithium/APE as an initiator for the anionic polymerization of methyl methacrylate, trapping by 4, and pyrolysis. These polymers could be reacted with amine‐functional polymers by melt blending, and the reaction progress could be monitored by gel permeation chromatography coupled with fluorescence detection. This technique not only allows monitoring of the coupling reaction with high sensitivity (ca. 100 times more sensitive than refractive index detection) but also permits selective detection because unlabeled polymers are invisible to fluorescence detection. This highly sensitive and selective detection methodology was also used to monitor the coupling reaction of 8 with PS‐NH₂ at a thin‐film interface, which was otherwise difficult to detect by conventional methods. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 2177–2185, 2000     

Synthesis of di‐ and tetra‐adducts by addition of polystyrene macroradicals onto fullerene C60

Br‐terminated polystyrenes of controlled molar masses and low polydispersities prepared by atom transfer radical polymerization (ATRP) can be converted to macroradicals using an appropriate catalytic complex (CuBr/bipyridine/100 °C). The addition of this macroradicals PS° to 6–6 bonds of C₆₀ follows a specific atom transfer radical addition mechanism that favors the grafting of even number of chains onto the fullerene core. This peculiar mechanism, resulting from the properties of C₆₀, offers an easy synthetic route toward well‐defined di‐ and tetra‐adducts. In these adducts the disturbance of the electronic structure of the fullerene is kept at its minimum, as only one double bond needs to be opened on the C₆₀ to add two PS chains and only two double bonds are converted to single bonds in the tetra‐adduct. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 3456–3463, 2004