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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.

An heterofunctional initiator combining two reactive sites for ring opening polymerization and two for atom transfer radical polymerization was used to prepare three A2B2 miktoarm star copolymers of poly(e-caprolactone) (PCL) and polystyrene (PS). The morphology and thermal properties were studied by transmission electron microscopy, polarized light optical microscopy, and differential scanning calorimetry. The (PCL)2(PS)2 72/28 (72 wt % PCL) sample was crystallized from a disordered melt. In this case, crystallization drove the structure formation and a lamellar morphology was obtained at the microdomain level, while spherulites were observed at a superstructural level. The other two samples, 39/61 and 27/73, with lower PCL content and higher total molecular weight, were not able to form spherulites. Surprisingly, these miktoarm star copolymers exhibited hexagonally packed cylinders and spheres morphologies, respectively, instead of lamellar and cylindrical morphology. Such unexpected and novel behavior was explained in terms of the higher resistance of the arms to be stretched in a miktoarm star copolymer when compared with the corresponding linear diblocks. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5387–5397, 2007

Model copolymers of poly(butadiene) (PB) and poly(dimethylsiloxane) (PDMS), PB-b-PDMS-b-PB, were synthesized by sequential anionic polymerization (high vacuum techniques) of 1,3-butadiene and hexamethylciclotrisiloxane (D 3 ) on sec-BuLi followed by chlorosilane-coupling chemistry. The synthesized copolymers were characterized by nuclear magnetic resonance ( 1 H NMR), size-exclusion chromatography (SEC), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). SEC and 1 H NMR results showed low polydispersity indexes (M w /M n ) and variable siloxane compositions, whereas DSC and TGA experiments indicated that the thermal stability of the triblock copolymers depends on the PDMS composition.

Star polymers provide model architectures to understand the dynamic and rheological effects of chain confinement for a range of complex topological structures like branched polymers, colloids, and micelles. It is important to describe the structure of such macromolecular topologies using small-angle neutron and x-ray scattering to facilitate understanding of their structure-property relationships. Modeling of scattering from linear, Gaussian polymers, such as in the melt, has applied the random phase approximation using the Debye polymer scattering function. The Flory-Huggins interaction parameter can be obtained using neutron scattering by this method. Gaussian scaling no longer applies for more complicated chain topologies or when chains are in good solvents. For symmetric star polymers, chain scaling can differ from ν=0.5(d(f)=2) due to excluded volume, steric interaction between arms, and enhanced density due to branching. Further, correlation between arms in a symmetric star leads to an interference term in the scattering function first described by Benoit for Gaussian chains. In this work, a scattering function is derived which accounts for interarm correlations in symmetric star polymers as well as the polymer-solvent interaction parameter for chains of arbitrary scaling dimension using a hybrid Unified scattering function. The approach is demonstrated for linear, four-arm and eight-arm polyisoprene stars in deuterated p-xylene.

A novel highly efficient strategy, based on an “alliance” of primary and secondary amine initiators, was successfully developed allowing the fast and living ring-opening polymerization (ROP) of α-amino acid N-carboxyanhydrides (NCAs) at room temperature.

The discovery of living anionic polymerization by Szwarc 50 years ago opened the way to the synthesis of model polymers. This ground-breaking discovery inspired many researchers to develop controlled/living routes for a plethora of monomers including those not compatible with anionic polymerization. These methods and their combinations serve as an arsenal for the synthesis of well-defined polymeric materials with predetermined properties and a rich variety of applications. A few representative examples of living and controlled/living methodologies for the synthesis of polymers with different macromolecular architectures are presented in this review.

Novel hierarchical nanostructures based on ionically self-assembled complexes of diblock copolypeptides and surfactants are presented. Rod-coil diblock copolypeptide poly(gamma-benzyl-L-glutamate)-block-poly(L-lysine), PBLG-b-PLL (Mn = 25,000 and 8000 for PBLG and PLL, respectively, polydispersity index 1.08), was complexed with anionic surfactants dodecanesulfonic acid (DSA) or dodecyl benzenesulfonic acid (DBSA), denoted as PBLG-b-PLL(DSA)1.0 and PBLG-b-PLL(DBSA)1.0, respectively. The complexation leading to supramolecular rod-comb architectures was studied by transmission electron microscopy (TEM), small-angle X-ray scattering (SAXS), Fourier transform infrared spectroscopy (FTIR), and polarized optical microscopy (POM). PBLG-b-PLL, PBLG-b-PLL(DBSA)1.0, and PBLG-b-PLL(DSA)1.0 self-assemble with alternating PBLG lamellae and PLL-containing lamellae with a periodicity of 27-33 nm. Within the PBLG lamellae, the rod-like PBLG helices pack with a periodicity of ca. 1.3 nm. The internal structure of the PLL-containing lamellae depends on the complexation. For pure PBLG-b-PLL, the PLL chains adopt a random coil conformation and the PLL domains are disordered. For PBLG-b-PLL(DSA)1.0, lamellar self-assembly of periodicity of 3.7 nm within the PLL(DSA)1.0 domains is observed due to crystalline packing of the linear n-dodecyl tails. For PBLG-b-PLL(DBSA)1.0 with branched dodecyl tails, a distinct SAXS reflection is observed, suggesting self-assembly within the PLL(DBSA)1.0 domains with a periodicity of 2.9 nm. However, due to the absence of higher order reflections, the internal structure cannot be conclusively assigned. The efficient plasticization which leads to fluid-like liquid crystallinity in PBLG-b-PLL(DBSA)1.0 and an alpha-helical conformation according to FTIR allows us to suggest that the PLL(DBSA)1.0 domains have a hexagonal internal structure. The interplay of self-assembly at different length scales combined with rod-like liquid crystallinity can open new routes to design functional materials.

We investigate the linear rheology of model star-comb homopolymers consisting of star-like backbone chains with grafted branches. We show that the tube-based theory in the framework of full dynamic dilution, appropriately modified to account for the effects of the fluctuations of the free segments (the segments of the star arms between the outer branching points and the arms’ free end-monomers) of the backbone star arms, and the polydispersity accurately describes the linear viscoelastic spectrum. For these branched polymers, the relaxation is found to proceed hierarchically, similar to combs with linear backbones. However, in contrast to the latter, here, there is no reptation. The higher functionality star combs with sparse branching are particularly interesting because they resemble a Cayley tree structure and are treated in the context of asymmetric star polymers. We also employ solutions of star combs and test our model in static dilution conditions. In the region where despite the presence of both static (solvent) and dynamic dilution the polymers remain entangled, our model is particularly successful without adjusting any parameters.

Three- and four-arm star-block copolypeptides, (BL-b-G) 3 and (G-b-BL) 4 , of poly(e-butyloxycarbonyl-L-lysine) (BL) and poly(γ-benzyl-L-glutamate) (G), were synthesized under high vacuum conditions, using three different multifunctional amino-initiators for the ring opening polymerization of the corresponding α-aminoacid N-carboxyanhydrides. When the initiator contained only primary amine groups {2(aminomethyl)-2-methyl-1,3-propanediamine, AMPDA}, well-defined star-block copolypeptides with monomodal molecular weight distribution were produced. However, if the multifunctional initiator contained both primary and tertiary amine groups {polypropylenimine tetraamine dendrimer, generation 1.0 (DAB); amidoethylethanolamine dendrimer, 1,4-diaminobutane core, generation o.o (PAMAM)}, bimodal high polydispersed copolypeptides were formed. The different behaviors are due to the participation of both the primary and tertiary amino groups, each following different polymerization kinetics.

A series of well-defined second (G-2) and third (G-3) generation dendritic polybutadienes (PBd) were synthesized by the coupling of the living G-2 and G-3 dendrons with methyltrichlorosilane, using anionic polymerization high-vacuum techniques. The synthetic approach of the living G-2 dendrons involves (a) the synthesis of an in-chain double-bond PBd by selective replacement of the two chlorines of 4-(dichloromethylsilyl)diphenylethylene (DCMSDPE), a novel linking reagent with dual functionality, with PBd by titration with PBdLi, (b) addition of s-BuLi to the double bond, and finally (c) polymerization of butadiene from the newly created anionic site. The synthesis of the G-3 dendrons requires the repetition of the aforementioned procedure with the exception of the addition of the living G-2 dendron, instead of PBdLi, to DCMSDPE. Intermediate and final products were characterized via size exclusion chromatography, membrane osmometry, size exclusion chromatography equipped with a two-angle laser light scat...

Living anionic polymerization of 4-vinylbenzocylobutene was performed in benzene at room temperature using sec-butyllithium as the initiator. Results of the kinetic studies indicated the termination- and transfer-free nature of the polymerization. Homopolymers with predictable molecular weights and narrow molecular weight distributions were produced, excluding the interference of the cyclobutene rings during initiation and propagation. Thermogravimetric analysis of poly(4-vinylbenzocyclobutene) in air showed a small weight gain at ∼200 °C, a rapid decomposition at ∼455 °C, and a gradual decomposition at ∼566 °C. This behavior was attributed to the formation of radicals from the pendent benzocyclobutene functionality through o-quinodimethane intermediates and simultaneous decomposition/cross-linking reactions at high temperature. The living nature of the polymerization was also examined via sequential copolymerization with butadiene to form diblock copolymers.

Three 6-miktoarm star (6μ-star) copolymers [PS(P2MP)5] of styrene (S) and 2-methyl-1,3-pentadiene (2MP) were synthesized by anionic polymerization and controlled chlorosilane chemistry, using high vacuum techniques. In all cases [Mw = 103 kg/mol, [S] = 44% (v/v); Mw = 91.1 kg/mol, [S] = 53% (v/v); Mw = 224 kg/mol, [S] = 92% (v/v)] the P2MP exhibited high 1,4-microstructure (∼99%). Molecular characterization (size-exclusion chromatography, membrane osmometry, low-angle laser light scattering, and NMR) revealed high molecular weight/composition homogeneity, and structural analysis (differential scanning calorimetry, transmission electron microscopy, and small-angle X-ray scattering) showed highly ordered patterns. The deviations from predictions based on Milner's morphological model are much more pronounced than that of PS(P2MP)2 and PS(P2MP)3 miktoarm stars, which we attribute to greater crowding of the arms for these highly branched molecules.

PS-PI multigraft copolymers with tri- tetra- and hexafunctional polystyrene branch points have been studied to investigate the influence of molecular architecture on morphological and tensile properties and to find novel material concepts. It was found that the morphological behaviour of these grafted copolymers can be predicted using theoretical approaches. The number of branch points, however, greatly influences the long-range order of microphase separation. Additionally, two new parameters for adjusting mechanical properties of multigraft copolymers are found in our investigations: 1) functionality of the graft copolymer: tri-, tetra- or hexafunctional and 2) number of branch points per molecule. Tetrafunctional multigraft copolymers show surprising high strain at break values up to 1550 %. With increasing number of branch points strain at break and tensile strength increase, where a linear dependence of mechanical properties on the number of branch points is obvious. Excellent elasticity of tetra and hexafunctional multigraft copolymers at high deformation was proved in hysteresis experiments.

Model diblock copolymers of poly(1,4-butadiene) (PB) and poly(dimethylsiloxane) (PDMS), PB-b-PDMS, were synthesized by the sequential anionic polymerization (high vacuum techniques) of butadiene and hexamethylciclotrisiloxane (D3) in the presence of sec-BuLi. By homogeneous hydrogenation of PB-b-PDMS, the corresponding poly(ethylene) and poly(dimethylsiloxane) block copolymers, PE-b-PDMS, were obtained. The synthesized block copolymers were characterized by nuclear magnetic resonance (1H and 13C NMR), size-exclusion chromatography (SEC), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), transmission electron microscopy (TEM), and rheology. SEC combined with 1H NMR analysis indicates that the polydispersity index of the samples (Mw/Mn) is low, and that the chemical composition of the copolymers varies from low to medium PDMS content. According to DSC and TGA experiments, the thermal stability of these block copolymers depends on the PDMS content, whereas TEM analysis reveals ordered arrangements of the microphases. The morphologies observed vary from spherical and cylindrical to lamellar domains. This ordered state (even at high temperatures) was further confirmed by small-amplitude oscillatory shear flow tests. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1579–1590, 2006

A series of novel four-arm A2B2 and A2BC and five-arm A2B2C miktoarm star polymers, where A is poly(dimethylsiloxane) (PDMS), B is polystyrene (PS), and C is polyisoprene (PI), were successfully synthesized by the combination of chlorosilane and benzyl chloride linking chemistry. This new and general methodology is based on the linking reaction of in-chain benzyl chloride functionalized poly(dimethylsiloxane) (icBnCl–PDMS) with the in-chain diphenylalkyl (icD) living centers of PS-DLi-PS, PS-DLi-PI, or (PS)2-DLi-PI. icBnCl–PDMS was synthesized by the selective reaction of lithium PDMS enolate (PDMSOLi) with the chlorosilane groups of dichloro[2-(chloromethylphenyl)ethyl]methylsilane, leaving the benzyl chloride group intact. The icD living polymers, characterized by the low basicity of DLi to avoid side reactions with PDMS, were prepared by the reaction of the corresponding living chains with the appropriate chloro/bromo derivatives of diphenylethylene, followed by a reaction with BuLi or the living polymer. The combined molecular characterization results of size exclusion chromatography, 1H NMR, and right-angle laser light scattering revealed a high degree of structural and compositional homogeneity in all miktoarm stars prepared. The power of this general approach was demonstrated by the synthesis of a morphologically interesting complex miktoarm star polymer composed of two triblock terpolymer (PS-b-PI-b-PDMS) and two diblock copolymer (PS-b-PI) arms. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 6587–6599, 2006

A combination of anionic and nitroxide-mediated radical polymerizations (dual initiator) was employed for the synthesis of poly(n-hexyl isocyanate-b-N-vinylpyrrolidone) (PHIC-b-PNVP) block copolymers. The samples were characterized with a size exclusion chromatograph equipped with refractive-index and light scattering detectors as well as 1 H NMR spectroscopy. Relatively good control over the molecular weights was achieved. However, rather broad molecular weight distributions were obtained. The micellar properties of the PHIC-b-PNVP block copolymers were studied in water, which is a selective solvent for the poly(N-vinylpyrrolidone) blocks. Static and dynamic light scattering revealed the presence of equilibrium between the micelles and clusters. The clusters partially deaggregated with increasing temperature.

Using Tapping Mode atomic force microscopy, we studied crystallization of polymers in confined cylindrical geometries of micro-phase separated asymmetric diblock copolymers, deposited in thin films onto solid substrates. We observed that in most cases crystallization occurs separately and independently in each cylinder of the mesophase pattern. We followed the kinetics of the crystallization process with time and found an influence of the lateral size of the cylindrical morphology on the rate of crystallization. The present data are compared to previous results on spherical mesophase patterns. The growth rate within one single cylinder was found to be not necessarily constant. Depending on the amount of crystallized material and the molecular weight, structural relaxations of the crystals can have very strong influence on the amorphous matrix and can even lead to the destruction of the mesophase pattern, allowing for break-out crystallization. As a consequence of break-out crystallization, crystallization kinetics changed considerably since the crystal growth was not limited anymore to the confinement imposed by the cylinders.

Three 4-miktoarm star quarterpolymers (4μ-SIDV), where S is polystyrene (PS), I polyisoprene-1,4 (PI), D poly(dimethylsiloxane) (PDMS), and V poly(2-vinylpyridine) (P2VP), were synthesized by anionic polymerization high-vacuum techniques. 4-(Dichloromethylsilyl)diphenylethylene (DCMSDPE), a dual-functionality compound with two SiCl groups (linking agent) and a nonhomopolymerizable double bond (diphenylethylene), was used as the nodule for the incorporation of the four incompatible arms. The synthetic approach involves selective replacement of the two chlorines of DCMSDPE with PI and PDMS by titration with the corresponding living chains, addition of the third arm PSLi to the in-chain double bond of the PI/PDMS intermediate, and finally polymerization of 2VP from the newly formed anionic site to create the fourth arm. Careful extraction/fractionation of the reaction products led to 4μ-SIDV stars with high molecular weight/compositional homogeneity, as proved by size exclusion chromatography, membrane osmom...

Amphiphilic cylindrical brush-coil block copolymers consisting of a polystyrene coil and a cylindrical brush block with poly(acrylic acid) side chains are prepared by ATRP of t-butylacrylate from a block comacroinitiator. Upon acidolysis of the poly(t-butylacrylate), water-soluble polymers were obtained that were observed to form micelles consisting of 4-5 block copolymers on average in aqueous solution. The star-like nature of such micelles was clearly visualized by scanning force microscopy.

The dynamics of colloidal star—linear homopolymer mixtures is investigated by photon correlation spectroscopy. In dilute star solutions, osmotic forces due to the added polymers lead initially to a shrinkage of the stars and eventually, at higher polymer concentrations, to stable star clusters. Furthermore, concentrated glassy star solutions melt upon addition of small amounts of linear polymers, as manifested by the remarkable speed-up of the star self-diffusion. Quantitative description of the experimental findings is provided by calculations of the effective star-star pair potential.

The morphologies of a 3-miktoarm star terpolymer of isoprene (I), styrene (S), and dimethylsiloxane (D), 3μ-ISD, and its blends with PDMS and PS homopolymers, having a lower molecular weight than the corresponding blocks of the star, were studied. Combined EF-TEM and 3D electron tomography clearly revealed that three kinds of cylindrical structures, composed of three different blocks, joined to fill the space and that these cylinders were curved collectively into an arc. The grain size of this star terpolymer was extremely small compared with that of other known linear block copolymers. By blending the neat 3μ-ISD with a small quantity of PDMS homopolymer (5 wt %), the morphology remained the same, but the grain size increased dramatically. It seems that the PDMS homopolymer inserts into the PDMS phase of the star terpolymer and straightens the bent cylinders, thereby increasing long-range order. However, the extra PDMS accumulates in line defects, which if controlled could be beneficial as waveguides in ...

The segmental and terminal dynamics of the individual components in miscible blends of polyisoprene (PI) and polystyrene (d3PS) were characterized over a wide temperature range. Though the system has a large positive Flory−Huggins interaction parameter χ ∼ 0.1, it is miscible in the temperature range of study due to low molecular weight. 13C and 2H NMR relaxation measurements were performed to extract the segmental relaxation times. Pulse-gradient spin-echo NMR was used to determine the center-of-mass diffusion coefficients. Though the segmental dynamics of PI and PS components differ by more than 2 decades at Tg + 50 K in the blends, their terminal dynamics (in terms of monomeric friction coefficients) are essentially identical. We know of no other system with this behavior. The distinct component segmental dynamics can be reasonably interpreted by the Lodge/McLeish model. The unusual homogeneous terminal dynamics may be due to a large thermodynamic barrier to diffusion in this system. The monomeric fric...

Stryrenic macromonomers of polybutadienes (sMMB) were synthesized by selective reaction of living polybutadienes with the silyl chloride group of 4-(chlorodimethylsilyl)styrene. Anionic copolymerization of sMMBs with butadiene, in the presence of a randomizer (potassium 2,3-dimethyl-3-pentoxide randomizer), led to living random comb polybutadienes (PBCs). Taking advantage of the living character of the PBCs, a number of well-defined comb, star−comb, and comb-on-comb polybutadienes were synthesized by using high-vacuum techniques. All samples prepared were characterized by size exclusion chromatography (SEC) with DRI detector and SEC with two-angle laser light scattering detector (SEC-TALLS).

Using a series of AnBn miktoarm star block copolymers with different numbers of arms (n = 1, 2, 4, and 16), the effect of molecular architecture on the grain growth kinetics was investigated by ann...

The formation of finite-sized microgel particles was revealed by photon correlation spectroscopy in aqueous solutions of hydrophobically associative polyelectrolyte polystyrene-block-poly(sodium methacrylate)-block-polystyrene. Starting from the lowest polymer concentration (1 x 10 -6 g L -1 ) up to 1 g L -1 a single relaxation process dominates the spectrum of relaxation times of the polymer solutions. This dominant mode was attributed to the diffusive motion of supramolecular microgel particles with a size of about 100 nm. Above a polyelectrolyte concentration of 1.0 g.L -1 , the size of the microgel grows up to ca. 300 nm. At a polymer concentration 20 g.L -1 , macroscopic phase separation occurs: the liquid phase of the microgel-cluster solution coexists with the phase of the macroscopic gel.

Living anionic surface-initiated polymerization on flat gold substrates has been conducted to create uniform homopolymer and diblock copolymer brushes. A 1,1-diphenylethylene (DPE) self-assembled monolayer was used as the immobilized precursor initiator. n-BuLi was used to activate the DPE in tetrahydrofuran at –78 °C to initiate the polymerization of different monomers (styrene, isoprene, ethylene oxide, and methyl methacrylate). Poly(styrene) (PS) and poly(ethylene oxide) (PEO) in particular were first investigated as grafted homopolymers, followed by their copolymers, including poly(isoprene)-b-poly(methylmethacrylate) (PI-b-PMMA). A combined approach of spectroscopic (Fourier transform infrared spectroscopy, surface plasmon spectroscopy, ellipsometry, X-ray photoelectron spectroscopy) and microscopic (atomic force microscopy) surface analysis was used to investigate the formation of the polymer brushes in polar solvent media. The chemical nature of the outermost layer of these brushes was studied by water contact angle measurements. The effect of the experimental conditions (solvent, temperature, initiator concentration) on the surface properties of the polymer brushes was also investigated. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 769–782, 2006

3-Miktoarm star copolymers, 3μ-D2V, with two poly(dimethylsiloxane) (PDMS) and one poly(2-vinylpyridine) (P2VP) arm, were synthesized by using anionic polymerization–high vacuum techniques and (chloromethylphenylethyl)methyl dichlorosilane, heterofunctional linking agent, with two SiCl groups and one CH2Cl group. The synthetic strategy involves the selective reaction of the two SiCl groups with PDMSOLi living chains, followed by reaction of the remaining chloromethyl group with P2VPLi. Combined molecular characterization results (size exclusion chromatography, membrane osmometry, and 1H NMR spectroscopy) revealed a high degree of structural and compositional homogeneity. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 614–619, 2006

The synthesis of model linear and star double-comb polybutadienes, as well as molecular double-brush polybutadienes, with two tails emanating from each branch point, is presented. The synthetic approach involves (1) the selective reaction of living polybutadienes with the two chlorines of 4-(dichloromethylsilyl)styrene to make double-tailed macromonomers and (2) the homopolymerization or copolymerization of the double-tailed macromonomer, in situ without isolation, to produce the double brushes and double combs, respectively. The star double comb was synthesized by the reaction of living double-comb polybutadiene with trichloromethylsilane. Characterization carried out by size exclusion chromatography, with differential refractometer and light scattering detectors, indicated that the synthesized polybutadienes had a high degree of molecular and structural homogeneity. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4070–4078, 2005

Well-defined ω-cholesteryl poly(n-hexyl isocyanate) (PHIC-Chol), as well as diblock copolymers of n-hexyl isocyanate (HIC) with styrene, PS-b-PHIC [PS = polystyrene; PHIC = poly(n-hexyl isocyanate)], and triblock terpolymers with styrene and isoprene, PS-b-PI-b-PHIC and PI-b-PS-b-PHIC (PI = polyisoprene), were synthesized with CpTiCl 2 (OR) (R = cholesteryl group, PS, or PS-b-PI) complexes. The synthetic strategy involved the reaction of the precursor complex CpTiC1 3 with cholesterol or the suitable w-hydroxy homopolymer or block copolymer, followed by the polymerization of HIC. The ω-hydroxy polymers were prepared by the anionic polymerization of the corresponding monomers and the reaction of the living chains with ethylene oxide. The reaction sequence was monitored by size exclusion chromatography, and the final products were characterized by size exclusion chromatography (light scattering and refractive-index detectors), nuclear magnetic resonance spectroscopy, and, in the case of PHIC-Chol, differential scanning calorimetry.

The following block–comb/graft copolymers of styrene (S), isoprene (I), and butadiene (B)—PS-b-(PB-g-PB), PS-b-(PB-g-PB)-b-PS, (PB-g-PB)-b-P2VP, (PS-g-PB)-b-(PI-g-PS), (PS-g-PB)-b-(PI-g-PS)-b-(PB-g-PI), (PS-g-PB)-b-(PI-g-PS)-b-(PB-g-PI)-b-(PI-g-PS)-b-(PS-g-PB), and (PS)2(PB-g-PB) [where PS is polystyrene, PB is polybutadiene, P2VP is poly(2-vinylpyridine) (2VP), and PI is polyisoprene]—were synthesized with the macromonomer strategy and anionic polymerization high-vacuum techniques. The synthetic approach involves the synthesis and block copolymerization of styrenic macromonomers in situ without isolation. The prepared samples were characterized by size exclusion chromatography with a differential refractometer detector, size exclusion chromatography with a two-angle laser light scattering detector, and NMR spectroscopy. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4040–4049, 2005

Statistical copolymers of methyl methacrylate with cyclohexyl and trimethylsilyloxy ethyl methacrylate were synthesized with two different catalytic systems based on the zirconocene complex Cp2ZrMe2. The reactivity ratios of methyl methacrylate and these methacrylates were calculated with the Finemann–Ross, inverted Finemann–Ross, and Kelen–Tudos graphical methods. The structural parameters of these copolymers were estimated from the calculation of the dyad monomer sequence fractions. Two different borate cocatalysts were employed, and their effect on the copolymerization process is discussed. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3305–3314, 2005

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 LiBPh 4 , NaBPh 4 , and crown ether 18C6. The products were characterized by size exclusion chromatography (SEC), membrane osmometry (MO), and 1 H 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/NaBPh 4 in a molar ratio 1/10. By using BzNa/NaBPh 4 system, well-defined block copolymers of HIC with styrene or isoprene were synthesized for the first time.

The polymerization behavior of cyclohexyl methacrylate and trimethylsilyloxyethyl methacrylate with the catalytic system Cp2ZrMe2/B(C6F5)3/ZnEt2 was examined. Block copolymers of these bulky methacrylates with methyl methacrylate (MMA), having high molecular weights and relatively narrow molecular weight distributions, were prepared. n-Butyl acrylate and tert-butyl acrylate were polymerized with various catalytic systems based on zirconocene complexes. These polymerizations seemed to proceed to a nonquantitative yield, producing polymers with high molecular weights and relatively low polydispersities. This behavior indicated the presence of termination reactions in the initiation step, which appeared to be faster than the propagation step. Block copolymers of these acrylates with MMA were synthesized with the catalytic system rac-Et(Ind)2ZrMe2/[B(C6F5)4]−[Me2NHPh]+/ZnEt2, starting from the polymerization of MMA. The block copolymers produced were well defined in most cases, as indicated by size exclusion chromatography, NMR, and differential scanning calorimetry measurements. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3337–3348, 2005

We use a surface force balance (SFB) to study the normal interactions between polymer brushes, which are self-assembled from solution. They consist of polystyrene (PS) chains in toluene (neutral chains in a good solvent) anchored on the interacting mica surfaces via sulfozwitterionic end groups. The properties of the brush depend on the length, N, of the chain, and the energy, αk B T, with which the end group adsorbs on the surface. In contrast to earlier studies where N was varied, we attempt to vary the sticking energy by using polymer chains with one, two, and three zwitterions attached to their ends. We use the theory of Alexander and de Gennes to predict how the normal force profile should vary with a and N, finding, for example, that the brush height L 0 obeys L 0 = a . N 3/5 . α 2/5 . Surprisingly, our measurements show that the grafting density does not vary significantly between polymers with 1, 2, and 3 end groups. This could be attributed to dipole-dipole interactions between the zwitterions themselves. It is also possible that the effect could be kinetic: that the brush is unable to reach its equilibrium state because successive polymer chains are hindered from attaching to the surface by those already in the brush. Measurements on longer time scales will be necessary to determine whether kinetic effects are important.

Fourier-Transform rheology (FT rheology) was used to study the influence of the degree of branching on the nonlinear relaxation behaviour of polystyrene solutions. The results were compared with those obtained under oscillatory shear and step-shear conditions. The different topologies could be distinguished using FT rheology where the other rheological measurement faile. Significant differences occurred under large amplitude oscillatory shear (LAOS) conditions as particularly reflected in the phase difference of the third harmonic, Φ 3 , which could be related to strain softening and strain-hardening behaviour. Currently, this work is extended towards different topologies in polyolefins (e.g. long chain branched).

Multigraft copolymers with polyisoprene backbones and polystyrene branches, having multiple regularly spaced branch points, were synthesized by anionic polymerization high vacuum techniques and controlled chlorosilane linking chemistry. The functionality of the branch points (1, 2 and 4) can be controlled, through the choice of chlorosilane linking agent. The morphologies of the various graft copolymers were investigated by transmission electron microscopy and X-ray scattering. It was concluded that the morphology of these complex architectures is governed by the behavior of the corresponding miktoarm star copolymer associated with each branch point (constituting block copolymer), which follows Milner's theoretical treatment for miktoarm stars. By comparing samples having the same molecular weight backbone and branches but different number of branches it was found that the extent of long range order decreases with increasing number of branch points. The stress-strain properties in tension were investigated for some of these multigraft copolymers. For certain compositions thermoplastic elastomer (TPE) behavior was observed, and in many instances the elongation at break was much higher (2-3X) than that of conventional triblock TPEs.

13C NMR has been used to investigate the segmental dynamics of isolated polyisoprene (PI) chains in host matrices of polybutadiene (PB), poly(vinylethylene) (PVE), and polystyrene (PS). In the dilu...

High-resolution inelastic light scattering was employed to measure the dispersion relations for the acoustic excitations in ordered concentrated solutions of poly(styrene)-block-poly(isoprene) copolymers with both symmetric and asymmetric composition and large spacing (220−415 nm). The morphology is manifested in the rich phonon spectrum recorded for different scattering wave vectors q in the range 0.003−0.034 nm-1. The experimental ωs(q) of the sth branch is directly compared with the theoretical dispersion from band structure calculations performed for different directions of q in the reciprocal lattice of lamellar and cylindrical periodic structures. The dispersion relations turn out to be a sensitive index of the microphase morphology and the grain orientation.

ω-Lithium sulfonate polystyrene-block-polyisoprenes were synthezised by anionic polymerization high vacuum techniques and a post-polymerization reaction with 1,1-diphenylethylene and 1,3-propane sultone. The solution properties of ω-lithium sulfonate block copolymers were studied in a low polarity solvent (CCI 4 ) which is a good solvent for both blocks. The study revealed the formation of aggregates due to the association of the lithium sulfonate groups (SuLi). The mass, size and shape of the aggregates were studied by static and dynamic light scattering and viscometry. The aggregation number decreased as the lengh of the chain increased and the aggregates showed a behavior similar to that of star polymers. The micellization of ω-functionalized block copolymers was also studied in a polar selective solvent for polystyrene, N,N-dimethylacetamide (DMA). Micelles formed from block copolymers containing the sulfonate group at the polyisoprene end exhibited an association number which was about 80% of that of the neutral block copolymer and had a higher critical micelle concentration. The samples having the polar group at the PS end showed a similar behavior.

Statistical copolymers of methyl methacrylate (MMA) with n-butyl-, s- butyl, t-butyl-, n-hexyl-, decyl-, stearyl-, allyl-, trimethylsilyl- and trimethylsilyloxy- ethyl methacrylate were prepared by zirconocene-catalyzed copolymerization. The re- activity ratios of MMA copolymers with butyl-, hexyl-, and stearyl methacrylate were estimated using the Finemann-Ross, the inverted Finemann-Ross, and the Kelen- Tudos graphical methods. Structural parameters of the copolymers were obtained from the calculated dyad sequences, derived by using the reactivity ratios. The effect of the nature of the methacrylate ester group and the catalytic system used on the copolymer structure is discussed. The glass-transition temperature (Tg) values of MMA copoly- mers with butyl- and hexyl methacrylate were measured and examined in the frame of several theoretical equations, allowing the prediction of these Tg values. The best fit was obtained using Barton and Johnston equations, taking the monomer sequence distribution of the copolymers into account. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 3761-3774, 2004

The micellization properties of well-defined block copolymers of styrene and decyl methacrylate (SDMA) were studied in two different solvents, methyl acetate (MAc) selective for the polystyrene (PS) block and dodecane, selective for the poly(decyl methacrylate) (PDMA) block. The results were compared with those obtained, in the same solvents, from block copolymers of styrene and stearyl methacrylate (SSMA). In MAc, SDMA copolymers with a decyl methacrylate (DMA) content of 15% or less formed unimolecular micelles, whereas those with a content of 18.5% or higher formed multimolecular micelles. The degrees of association were lower than the corresponding SSMA samples. In dodecane, SDMA form large, monodisperse, spherical, and thermally stable micelles with degrees of association higher than the corresponding SSMA samples. The different behaviors can be attributed to the steric hindrance effect and the ability of the long alkyl groups of the polymethacrylate, MA blocks to crystallize. When the MA blocks are in the soluble corona of the micelles, the steric hindrance effect prevails, thus leading to higher degrees of association for the less bulky alkyl group. In the case where the MA block is in the insoluble core of the micelles, the higher the tendency for crystallization the higher the degree of association. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4177–4188, 2004

The micelles formed when a dendritic polymer of polystyrene (PS) and polyisoprene (PI), having the overall structure (PS2PI)3, were examined in two solvents, dimethylformamide (DMF) and dimethylacetamide (DMA). Both solvents are good solvents for polystyrene and non-solvents for polyisoprene. The aggregation behavior was studied by a combination of static and dynamic light scattering and viscometry. In both systems star-like micelles were formed which followed the hard sphere model. The aggregation number was much lower for the micelles formed in DMA. The polymer–solvent interaction parameters indicate that the interactions are stronger between both PS-DMA and PI-DMA than for either polymer block with DMF. The effects of solvent selectivity are exacerbated by the structure of the polymer. With each polymer molecule contributing six soluble arms to the micelle, in the better solvent (DMA) increased repulsive interactions between the extended polystyrene lead to lower aggregation numbers.

Graft copolymers having poly(methyl methacrylate), PMMA, backbone and polystyrene, PS, polyisoprene, PI, poly(ethylene oxide), PEO, poly(2-methyl-1,3-pentadiene), P2MP, and PS-b-PI branches were prepared using the macromonomer methodology and high-vacuum techniques. The methacrylic macromonomers, mMM, were synthesized by anionic polymerization, whereas their homopolymerization and copolymerization with MMA were performed by metallocene catalysts. Relatively high macromonomer conversions were obtained in all cases. The parameters affecting the polymerization characteristics were examined. Well-defined poly(butyl methacrylate)-b-poly(methyl methacrylate) block copolymers were prepared for the first time by sequential addition of monomers starting from n-butyl methacrylate. The samples were characterized by size exclusion chromatography, SEC, 1H and 13C NMR spectroscopy, low-angle laser light scattering, LALLS, and differential scanning calorimetry, DSC.

In addition to phase morphology, diffusion, and dynamics in the bulk, the behavior of block copolymers in the confined state has been of great interest. Although random and graft copolymers have been used in polymer-layered silicate nanocomposites, well-defined block copolymers have received relatively little attention. In this study, the kinetics of intercalation of a series of poly(styrene-b-isoprene) block copolymers into a layered silicate were examined via X-ray diffraction. Intercalation was observed even when the copolymer was in the ordered state, with no discontinuity around the order-disorder transition of the copolymer. As the size of the polystyrene block was increased, slower intercalation kinetics were observed, possibly because of the increased glass-transition temperature of the polystyrene segment. Finally, the clearing temperature of the copolymer in the nanocomposites as measured by small-angle X-ray scattering showed a large heating-rate dependence suggesting that the nanoparticles act as kinetics barriers to the disordering of the copolymer.

The efficiency of the macromonomer (MM) synthetic strategy for the creation of nonlinear complex macromolecular architectures (miktoarm stars, α,ω-branched polymers, random/exact comb and graft copolymers, dendritic polymers, molecular brushes) is reviewed. In addition, the solution/bulk properties and the potential applications of polymacromonomers (PMM), as well as new synthetic ideas are presented. The synthesis of macromonomers and living polymacromonomers in situ leads to many novel linear and nonlinear structures, as for example PMM-b-PS-b-PMM, (PS) 2 PMM. The use of multichlorosilylstryrenes as monomer/ linking agents opens new ways for structures with multichain macromonomeric building blocks.

Temperature gradient interaction chromatography (TGIC) was applied for the separation of a complex miktoarm star copolymer which has one polystyrene (PS) arm and three polystyrene-b-polyisoprene (PS-b-PI) diblock copolymer arms. Such miktoarm star polymers are much more difficult to characterize than branched homopolymers since the byproduct, typically polymers with missing arm(s) or coupled products, have not only different molecular weights but also different compositions. TGIC was able to fully separate the byproducts, and the composition of the molecular species corresponding to the different separated elution peaks was determined by two methods, fractionation/NMR and multiple detection (UV and RI). A reasonable agreement between the results of the two methods was obtained. By using the composition found, the corresponding molecular weights were determined by multi-angle light scattering detection. Based on the composition and the molecular weight we were able to identify the structure of the different molecular species.

The dynamics of designed short polyisoprene (PI) chains in the melt is investigated on a wide temperature window using dielectric relaxation spectroscopy and pulsed field gradient nuclear magnetic resonance (NMR). At high temperatures, molecular dynamics (MD) simulations performed using two different models (an explicit atom model and a united atom one) capture very well the dynamic properties documented experimentally. Structures pre-equilibrated with end-bridging Monte Carlo are used as initial configurations for MD runs at different temperatures, providing predictions for the temperature dependence of the dynamics of this bulk PI. Local dynamics is unique, independently of the probe (dielectric relaxation, dynamic light scattering, nuclear magnetic resonance, neutron scattering), although mean correlation times are significantly affected, to different extents, by librations. Chain dynamics over the molecular weight and temperature range studied can be described well by the Rouse model, as shown by both...

Triblock copolymers and pentablock terpolymers of n-hexyl isocyanate (H), styrene (S), and isoprene (I) of the type HSH (six samples, Mn:49–163 K, weight % of H:5–59), HIH (two samples, Mn:75 and 83.4 K, weight % of H:16 and 40), HSISH (one sample, Mn:79.4 K, weight % of H:13), and HISIH (one sample, Mn:128 K, weight % of H:25) were synthesized by high-vacuum techniques in tetrahydrofuran at −98 °C with the sodium naphthalene/sodium tetraphenylborate initiating system. All materials were characterized by size exclusion chromatography, membrane osmometry, and 1H NMR. The combined molecular characterization results revealed a high degree of molecular and compositional homogeneity. The thermal properties of the synthesized materials were examined by thermogravimetric analysis and differential scanning calorimetry. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3094–3102, 2003