Miktoarm Star Copolymers Research Articles

Hierarchical self-assembly of miktoarm star polymers containing a polycationic segment: A general concept

We recently introduced a concept for the counterion-mediated hierarchical self-assembly of an amphiphilic ABC miktoarm star terpolymer in aqueous media into micrometer-sized compartmentalized particles with a highly periodic lamellar fine structure (“woodlice”). Herein, we extend this concept to different miktoarm star polymer systems containing a polycationic segment. The presence of a poly(N-methyl-2-vinylpyridinium) (P2VPq) block and its interaction with iodide/triiodide counterions is crucial. In analogy to linear diblock copolymer systems the hydrophilic/hydrophobic balance of polybutadiene-arm-poly(N-methyl-2-vinylpyridinium iodide)-arm-polystyrene miktoarm star terpolymers determines the morphology of the primary building blocks (spherical micelles and cylindrical micelles/vesicles) and the obtained superstructures (stacked lamellar structures and multilamellar vesicles) during this hierarchical process. When an ABA' miktoarm star copolymer (polystyrene-arm-poly(N-methyl-2-vinylpyridinium iodide)-arm-polystyrene) without a dynamic core-forming block was investigated, a different mechanism into “woodlouse” structured aggregates via aggregation and deformation of intermediate vesicles was found. The individual steps of the different self-assembly processes were investigated by transmission electron microscopy and additionally supported by dynamic light scattering, differential scanning calorimetry, and small-angle X-ray scattering.

Stimuli‐responsive star polymers

ABSTRACTStimuli‐responsive star polymers gain more and more interest over the last decades due to their unique properties compared to their linear counterparts. The branched structure for instance has influence on the responsive behavior of these polymers. This review offers an overview of stimuli‐responsive star polymers generated by different polymerization techniques, e.g. anionic and controlled radical polymerization (CRP). Beside conventional branched homopolymers different other types like block copolymers, miktoarm star copolymers, core crosslinked star polymers (CCS) and comb polymers are also presented. Furthermore their responsive behavior in solution or immobilized on a substrate, and their applications are outlined. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 2980–2994

Drug and plasmid DNA co-delivery nanocarriers based on abctype polypeptide hybrid miktoarm star copolymers

We report on the fabrication of self-assembled micelles from ABC-type miktoarm star polypeptide hybrid copolymers consisting of poly(ethylene oxide), poly(L-lysine), and poly(ɛ-caprolactone) arms, PEO(-b-PLL)-b-PCL, and their functional applications as co-delivery nanocarriers of chemotherapeutic drugs and plasmid DNA. Miktoarm star copolymer precursors, PEO(-b-PZLL)-b-PCL, were synthesized at first via the combination of consecutive “click” reactions and ring-opening polymerizations (ROP), where PZLL is poly(ɛ-benzyloxycarbonyl-L-lysine). Subsequently, the deprotection of PZLL arm afforded amphiphilic miktoarm star copolymers, PEO(-b-PLL)-b-PCL. In aqueous media at pH 7.4, PEO(-b-PLL)-b-PCL self-assembles into micelles consisting of PCL cores and hydrophilic PEO/PLL hybrid coronas. The hydrophobic micellar cores can effectively encapsulate model hydrophobic anticancer drug, paclitaxel; whereas positively charged PLL arms within mixed micellar corona are capable of forming electrostatic polyplexes with negatively charged plasmid DNA (pDNA) at N/P ratios higher than ca. 2. Thus, PEO(-b-PLL)-b-PCL micelles can act as co-delivery nanovehicles for both chemotherapeutic drugs and genes. Furthermore, polyplexes of pDNA with paclitaxel-loaded PEO(-b-PLL)-b-PCL micelles exhibited improved transfection efficiency compared to that of pDNA/blank micelles. We expect that the reported strategy of varying chain topologies for the fabrication of co-delivery polymeric nanocarriers can be further applied to integrate with other advantageous functions such as targeting, imaging, and diagnostics.

Molecular dynamics in PBA/PEO miktoarm star copolymers

Molecular dynamics of miktoarm star copolymers consisting of poly(n-butyl acrylate) PBA and polyethylene oxide (PEO) arms was studied by means of Broadband Dielectric Spectroscopy (BDS) and Nuclear Magnetic Resonance (NMR) methods. The spectroscopic studies were performed for three types of copolymers differing in the composition, namely materials containing 76%, 46% and 16% molar fraction of PBA arms. The local processes, described by the Arrhenius law (e.g. the anisotropic rotation of methyl groups and the anisotropic local motions in the PEO chain), were observed for the studied systems below the glass transition temperature. It was found that the investigated PBA/PEO miktoarm star copolymers are characterized by single glass transition, which may result from similar values of glass transition temperatures of the PBA and PEO polymers. The segmental dynamics in the studied systems was quantitatively described by using the Vogel-Fulcher-Tammann (VFT) relation applied to combined NMR and BDS data. Moreover, above the glass transition temperature the interfacial polarization and conductivity phenomena were detected with the BDS method for all systems under study.

Synthesis and characterization of resorcinarene-centered amphiphilic A8B4miktoarm star copolymers based on poly(ε-caprolactone) and poly(ethylene glycol) by combination of CROP and “click” chemistry

Well-defined amphiphilic A8B4 miktoarm star copolymers with eight poly(ethylene glycol) chains and four poly(ε-caprolactone) arms (R-8PEG-4PCL) were prepared using “click” reaction strategy and controlled ring-opening polymerization (CROP). First, multi-functional precursor (R-8N3-4OH) with eight azides and four hydroxyls was synthesized based on the derivatization of resorcinarene. Then eight-PEG-arm star polymer (R-8PEG-4OH) was prepared through “click” reaction of R-8N3-4OH with pre-synthesized alkyne-terminated monomethyl PEG (mPEG-A) in the presence of CuBr/N,N,N′,N″,N″′- pentamethyldiethylenetriamine (PMDETA) in DMF. Finally, R-8PEG-4OH was used as tetrafunctional macroinitiator to prepare resorcinarene-centered A8B4 miktoarm star copolymers via CROP of ε-caprolactone utilizing Sn(Oct)2 as catalyst at 100 °C. These miktoarm star copolymers could self-assemble into spherical micelles in aqueous solution with resorcinarene moieties on the hydrophobic/hydrophilic interface, and the particle sizes could be controlled by the ratio of PCL to PEG. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 2824–2833.

Microstructures and phase transitions of A(BC)4 miktoarm star copolymers

The microstructures that self-assemble from A(BC)4 miktoarm star copolymers were investigated by self-consistent field theory. By tuning the interaction parameters between the different components and the volume fractions of the A, B, and C blocks, eleven kinds of highly ordered microstructures as well as a series of order–order and order–disorder transitions were observed. Triangle phase diagrams were constructed to show the different phase regions where a particular microstructure is stable. Our results show that tuning the interaction parameters and volume fractions of the blocks represents an effective control mechanism for obtaining desired microstructures.

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

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

Synthesis and molecular characterization of polythiophene and polystyrene copolymers: Simultaneous preparation of diblock and miktoarm copolymers

During the synthesis of polystyrene-b-polythiophene diblock copolymers (PS-b-PT) via combination of anionic polymerization (PS block) and polymerization of thiophene with iron trichloride (PT block), the simultaneous preparation of another product is observed and verified as a miktoarm star copolymer of the (PS)2PT type. This parallel synthesis is initially detected through size exclusion chromatography studies and then, after the complete separation of the two different products, it is certified by 13C NMR spectroscopy. IR and UV–Vis spectra of the two different products also display characteristic peaks for the PT chains, leading to proof of its presence in both cases. Furthermore, the products are studied thermally by thermogravimetric analysis and their morphology is preliminarily investigated by scanning electron microscopy.

Sub-10 nm Nano-Organization in AB2- and AB3-Type Miktoarm Star Copolymers Consisting of Maltoheptaose and Polycaprolactone

The AB2- and AB3-type miktoarm star copolymers consisting of maltoheptaose (MH, as A block) and poly(e-caprolactone) (PCL, as B block), namely MH-b-(PCL)2 and MH-b-(PCL)3, were synthesized, and their nano-organization was characterized. The syntheses of MH-b-(PCL)2 and MH-b-(PCL)3 were carried out through two reaction steps: (1) preparation of linear and three-branched PCLs bearing an azido group on the chain center (N3-(PCL)2 and N3-(PCL)3) by the diphenyl phosphate-catalyzed ring-opening polymerization of e-caprolactone (e-CL) using azido-functionalized di- and triols (N3-(OH)2 and N3-(OH)3) as the initiators and (2) the copper-catalyzed azide–alkyne cycloaddition of N3-(PCL)2 and N3-(PCL)3 with the ethynyl-functionalized MH. The miktoarm star copolymers having Mn for the PCL block of ca. 5000 (MH-b-(PCL2.5k)2 and MH-b-(PCL1.7k)3) and 10 000 (MH-b-(PCL5k)2 and MH-b-(PCL3.3k)3) were obtained with a very narrow polydispersity index of less than 1.05. Bulk samples of the four types of miktoarm star copolym...

Thermoresponsive Micellization and Micellar Stability of Poly(N-isopropylacrylamide)-b-DNA Diblock and Miktoarm Star Polymers

Linear and miktoarm star-shaped diblock copolymers consisting of single-stranded DNA and poly(N-isopropylacrylamide) (PNIPAAm) with various compositions were synthesized via atom transfer radical polymerization and click chemistry. The temperature-responsive phase transition behavior, micellization, was systematically examined using UV-vis spectrometry, high-sensitivity differential scanning calorimetry, dynamic light scattering, and small-angle X-ray scattering. The lower critical solution temperature (LCST) increased, and its enthalpy decreased with decreasing PNIPAAm content. The copolymers self-assembled into well-defined nanoparticles having a core composed of PNIPAAm and a coronal layer of DNA above LCST. The particle size and micellar aggregation number of copolymer chains depended on the macromolecular composition and chain architecture. On the other hand, regardless of their factors, the surface area occupied by one DNA strand was found to be almost unchanged. The hybridization of DNA on the nanoparticles with fully complementary one induced the aggregation of the particles in a non-cross-linking configuration. The nanoparticle composed of miktoarm star copolymer showed a quicker DNA-hybridization response in this non-cross-linking aggregation compared with the case of a linear analogue.

Morphology and NMR Self-Diffusion in PBA/PEO Miktoarm Star Copolymers

Abstract Morphology and NMR self-diffusion of two miktoarm star copolymers differing in fraction of poly(n-butyl acrylate) and poly(ethylene oxide) (PBA and PEO) arms were under investigation. Structural characteristics of copolymers was obtained on the basis of Small Angle X-Ray Scattering (SAXS) investigations. The phase separated nanoscale morphology of the miktoarm star copolymer with a high fraction of PEO arms was confirmed by Scanning Probe Microscopy (SPM) studies. The modified Avrami approach was used to obtain the information on the non-isothermal crystallization kinetics of the studied systems. It was observed that the crystallization in the system with a higher content of PBA, occurring at higher undercooling, was characterized by a higher crystallization rate. It was also found that increase in PBA arms fraction leads to the reduction in the size of PEO domains. The activation energy of the crystallization process, estimated with Kissinger's method, is lower for miktoarm star copolymer with higher PBA content, which results from facilitation of the transport of PEO chains in the direction of the growing crystal due to the presence of mobile PBA arms. The self-diffusion studies of miktoarm star copolymers melts, carried out with the Pulsed-Gradient STimulated-Echo (PGSTE) Nuclear Magnetic Resonance (NMR) technique, reveals the existence of at least two types of diffusion mechanisms in these systems.

Smart nanocarriers for pH-triggered targeting and release of hydrophobic drugs

The use of hybrid pH-sensitive micelles based mainly on the (PEO)129(P2VP)43(PCL)17 ABC miktoarm star copolymer as potential triggered drug delivery systems was investigated. Co-micellization of this star copolymer with a second copolymer labeled by a targeting ligand, i.e. biotin, on the pH sensitive block (poly-2-vinylpyridine) is considered here in order to impart possible active targeting of the tumor cells. Two architectures were studied for these labeled copolymers, i.e. a miktoarm star or a linear ABC terpolymer, and the respective hybrid micelles are compared in terms of cytotoxicity (cells viability) and cellular uptake (using fluorescent dye loaded micelles). Finally, the triggered drug release in the cytosol of tumor cells was investigated by studying, on the one hand, the lysosomal integrity after internalization and, on the other hand, the release profile in function of the pH.

Utility of Chromatographic and Spectroscopic Techniques for a Detailed Characterization of Poly(styrene-b-isoprene) Miktoarm Star Copolymers with Complex Architecture

We analyzed various miktoarm star copolymers of the PS(PI)x type (x = 2, 3, 5, 7), which consist of one long polystyrene (PS) arm (82 or 105 kDa) and various numbers of short polyisoprene (PI) arms (from 11.3 to 39.7 kDa), prepared by anionic polymerization and selective chlorosilane chemistry. The length of the PI arm in stars decreases with the number of arms, so that the chemical compositions of all PS(PI)x samples were comparable. Our aim was to determine the purity of samples and to identify exactly the constituents of individual samples. For this purpose we used a variety of separation techniques (size-exclusion chromatography (SEC), reversed-phase liquid-adsorption chromatography (RP-LAC), and two-dimensional liquid chromatography (2D-LC)) and characterization techniques (UV-MALS-RI multidetection SEC system, NMR, and MALDI-TOF MS). The best separation and identification of the samples’ constituents were achieved by RP-LAC, which separates macromolecules according to their chemical composition, and...

Synthesis and pyrolysis of ABC type miktoarm star copolymers with polystyrene, poly(lactic acid) and poly(ethylene glycol) arms

An ABC type miktoarm star copolymer possessing polystyrene (PS), poly(lactic acid) (PLA) and poly(ethylene glycol) (PEG) arms was synthesized by combining Atom Transfer Radical Polymerization (ATRP) and Ring Opening Polymerization (ROP) with two click chemistries, namely thiol–ene and copper catalyzed azide–alkyne cycloaddition (CuAAC). For this purpose, a core 1-(allyloxy)-3-azidopropan-2-ol with allyl and azide functionalities was synthesized in two steps. Then, clickable polymers, polystyrene with thiol functionality (PS–SH) and poly(ethylene glycol) with alkyne functionality (PEG–acetylene) were independently prepared. As the first step of the grafting onto process, PS–SH was thiol–ene clicked onto the core to yield PS–N3–OH. The second arm was then incorporated onto the core by the Ring Opening Polymerization (ROP) of l-(−)-Lactide (LA) using as PS–N3–OH initiator and tin(II) 2-ethylhexanoate as catalyst. Finally, alkyne–PEG–acetylene was bonded to the resulting PLA–PS–N3 using CuAAC click reaction. All intermediates, related polymers at different stages and final PS–PLA–PEG miktoarm star copolymer were characterized by 1H NMR, FT-IR, SEC and DP-MS analyses. Direct pyrolysis mass spectrometry, (DP-MS) analyses of PS–PLA–PEG and all intermediate polymers indicated that the decomposition of PS and PEG chains occurred almost independently, following the degradation mechanisms of the corresponding homopolymers. On the other hand, during the pyrolysis of PS–PLA–PEG, elimination of H2O during the decomposition of PEG chains at the early stages of pyrolysis caused hydrolysis of PLA chains and increased the yields of CO2, CO and units involving unsaturation and/or crosslinked structure.

Synthesis of Polyisobutylene-Based Miktoarm Star Polymers from a Dicationic Monoradical Dual Initiator

A dicationic monoradical dual initiator 3-[3,5-bis(1-chloro-1-methylethyl)phenyl]-3-methylbutyl 2-bromo-2-methylpropionate (DCCBMP) was designed for the preparation of A2B type miktoarm star copolymers, where A is a polyisobutylene (PIB)-based homo or block copolymer that is produced by living carbocationic polymerization (LCP), and B is a polyacrylate or other polymer block produced by atom transfer radical polymerization (ATRP). DCCBMP was obtained by chlorination of 3-[3,5-bis(1-hydroxy-1-methylethyl)phenyl]-3-methylbutyl 2-bromo-2-methylpropionate (DCOHBMP), which was synthesized in a pure form via aerobic oxidation of 3-(3,5-diisopropylphenyl)-3-methylbutyl 2-bromo-2-methylpropionate using N-hydroxyphthalimide (NHPI)/Co(OAc)2·4H2O catalyst system. Initiation efficiency of DCCBMP was 0.89–0.98 for LCP of isobutylene (IB) at −70 °C targeting molecular weights of 5K, 10K, and 20K g/mol, which was comparable to the standard dicationic initiator 5-tert-butyl-1,3-(1-chloro-1-methylethyl)benzene (t-Bu-m-DCC). Sequential monomer addition under LCP conditions produced narrow-polydispersity poly(styrene-b-isobutylene-b-styrene) (PS–PIB–PS) triblock copolymers. These polymers possessed a 2-bromo-2-methylpropionate (bromoester) ATRP initiating site in the approximate middle of PIB segment and two sec-benzylic chloride groups at the PS chain ends, which were also effective in initiating ATRP. With these PS–PIB–PS macroinitiators, poly(tert-butyl acrylate-b-styrene-b-isobutylene)2-s-poly(tert-butyl acrylate) [(PtBA–PS–PIB)2-s-PtBA] miktoarm star polymers were readily synthesized via ATRP of tert-butyl acrylate (tBA). The sec-benzylic chloride functionality was alternatively eliminated at high temperature (180–200 °C) under vacuum, yielding PS–PIB–PS macroinitiators containing only the bromoester site (thermolyzed PS–PIB–PS). Size exclusion chromatography (SEC) and nuclear magnetic resonance (NMR) spectroscopy showed that thermolysis removed all sec-benzylic chlorides without destruction of bromoester moieties. Thermolyzed PS–PIB–PS allowed synthesis of poly(styrene-b-isobutylene)2-s-poly(tert-butyl acrylate) [(PS–PIB)2-s-PtBA] star polymers with the potential hydrophilic segment attached only to the core of PS–PIB–PS. For both star terpolymer configurations, the PtBA blocks were converted to PAA via thermolysis at 150 °C to produce amphiphilic PIB-based miktoarm star polymers with narrow polydispersity indices (<1.1).

Synthesis of miktoarm star copolymer Ru(II) complexes by click-to-chelate approach

A series of AB2-, ABC-, (AB)2-, A2B2- and ABCD-type miktoarm star copolymer Ru(II) complexes were readily synthesized by stepwise chelating reactions between a Ru(II)(DMSO)4Cl2 and polymer-substituted 2-(1H-1,2,3-triazol-4-yl)pyridine or 2,6-bis(1H-1,2,3-triazol-4-yl)pyridine ligands. The polymer-substituted 2-(1H-1,2,3-triazol-4-yl)pyridine and 2,6-bis(1H-1,2,3-triazol-4-yl)pyridine ligands were conveniently prepared by the click reaction of ethynylpyridines with well-defined azido-terminated polymers, which were prepared by a combination of living/controlled polymerization procedures and end-substitution reactions.

Three‐arm star block copolymers of aromatic polyether and polystyrene from chain‐growth condensation polymerization, atom transfer radical polymerization, and click reaction

AbstractWell‐defined (AB)3 type star block copolymer consisting of aromatic polyether arms as the A segment and polystyrene (PSt) arms as the B segment was prepared using atom transfer radical polymerization (ATRP), chain‐growth condensation polymerization (CGCP), and click reaction. ATRP of styrene was carried out in the presence of 2,4,6‐tris(bromomethyl)mesitylene as a trifunctional initiator, and then the terminal bromines of the polymer were transformed to azide groups with NaN3. The azide groups were converted to 4‐fluorobenzophenone moieties as CGCP initiator units by click reaction. However, when CGCP was attempted, a small amount of unreacted initiator units remained. Therefore, the azide‐terminated PSt was then used for click reaction with alkyne‐terminated aromatic polyether, obtained by CGCP with an initiator bearing an acetylene unit. Excess alkyne‐terminated aromatic polyether was removed from the crude product by means of preparative high performance liquid chromatography (HPLC) to yield the (AB)3 type star block copolymer (Mn = 9910, Mw/Mn = 1.10). This star block copolymer, which contains aromatic polyether segments with low solubility in the shell unit, exhibited lower solubility than A2B or AB2 type miktoarm star copolymers. In addition, the obtained star block copolymer self‐assembled to form spherical aggregates in solution and plate‐like structures in film. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012

Water-Soluble Poly(vinylferrocene)-b-Poly(ethylene oxide) Diblock and Miktoarm Star Polymers

We describe the synthesis of water-soluble diblock and miktoarm star polymers consisting of poly(vinylferrocene) (PVFc) and poly(ethylene oxide) (PEO) blocks. First, end-functionalized poly(vinylferrocene) was generated by end-capping the living carbanionic PVFc chains with benzyl glycidyl ether (BGE) or ethoxy ethyl glycidyl ether (EEGE). Acidic hydrolysis of the EEGE-terminated PVFc partially oxidized the PVFc backbone. However, the dihydroxyl end-functional PVFc was obtained in quantitative yields by hydrogenolysis of the BGE-terminated PVFc. A series of block copolymers and AB2 miktoarm star copolymers was obtained in a second polymerization step, utilizing the respective end-functionalized PVFc as a macroinitiator for the ring-opening polymerization (ROP) of ethylene oxide. All polymers were analyzed in detail, using NMR spectroscopy and size-exclusion chromatography (SEC). Online SEC-viscosimetry as well as MALLS was carried out, confirming the formation of miktoarm structures. Quantitative function...

Degradable poly(ester-ether urethane)s derived of AB2 miktoarm star copolymer poly(ethylene glycol-(ε-caprolactone)2) diol: Synthesis, characterization and degradation

Four different miktoarm star copolymers poly(ethylene glycol-(ε-caprolactone)2) diol [PEG-PCL2] were obtained using α-diol-ω-methoxy poly(ethylene glycol) [MPEG-(OH)2] as macroinitiator/chain transfer agent in the ring opening polymerization (ROP) of ε-caprolactone (CL) catalyzed by tin(II) 2-ethylhexanoate [Sn(Oct)2]. PEG-PCL2 and 1,6-hexamethylene diisocyanate (HDI) were used as precursors of a new family of poly(ester-ether urethane)s PEUs. PEUs films were characterized by FT-IR, DSC, mechanical properties, water absorption, hydrolytic degradation and SEM.

Side-Chain-Controlled Self-Assembly of Polystyrene–Polypeptide Miktoarm Star Copolymers

We show how the self-assembly of miktoarm star copolymers can be controlled by modifying the side chains of their polypeptide arms, using A2B and A2B2 type polymer/polypeptide hybrids (macromolecular chimeras). Initially synthesized PS2PBLL and PS2PBLL2 (PS, polystyrene; PBLL, poly(e-tert-butyloxycarbonyl-l-lysine)) miktoarms were first deprotected to PS2PLLHCl and PS2PLLHCl2 miktoarms (PLLHCl, poly(l-lysine hydrochloride)) and then complexed ionically with sodium dodecyl sulfonate (DS) to give the supramolecular complexes PS2PLL(DS) and PS2(PLL(DS))2. The solid-state self-assemblies of these six miktoarm systems were studied by transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), and small- and wide-angle X-ray scattering (SAXS, WAXS). The side chains of the polypeptide arms were observed to have a large effect on the solubility, polypeptide conformation, and self-assembly of the miktoarms. Three main categories were observed: (i) lamellar self-assemblies at the block c...