Amphiphilic polymer conetworks are cross-linked polymers that swell both in water and in organic solvents and can phase separate on the nanoscale in the bulk or in selective solvents. To date, however, this phase separation has only been reported with short-range order, characterized by disordered morphologies. We now report the first example of amphiphilic polymer conetworks, based on end-linked "core-first" star block copolymers, that form a lamellar phase with long-range order. These mesoscopically ordered systems can be produced in a simple fashion and exhibit significantly improved mechanical properties. P olymeric hydrogels consist mostly of water held in place by a hydrophilic polymer matrix. They possess both liquidand solid-like characteristics. While these materials do not flow, they are very soft and allow the free diffusion of solutes. Furthermore, the high water content usually leads to biocompatibility. Extensively studied over the past 50 years, 1 hydrogels find uses as superabsorbents 2,3 (packing material in hygienic and baby diapers, media for water retention in agriculture and wastewater management), in medicine 4 (vehicles for controlled drug delivery 5 and as scaffolds for tissue engineering 6 ), in biotechnology 7 (matrices for enzyme immobilization and media for electrophoresis), as soft contact lenses, 8 and in sensors and actuators. 9 Amphiphilic polymer conetworks (APCNs), first reported in 1988 by Kennedy 10 and Stadler, 11 are related to hydrogels and have received increased attention in the past 10−15 years. 12 APCNs are composed of covalently interconnected hydrophilic and hydrophobic segments, swell in both polar and nonpolar solvents, and can solubilize both polar and nonpolar solutes. Furthermore, the arrangement of each type of units in relatively long sequences results in APCN self-assembly in selective solvents, very much like the micellization of conventional lowmolecular-weight surfactants and linear amphiphilic block copolymers, and the creation of a large interfacial area. 13 This internal self-organization differentiates APCNs from simple hydrogels and enables them for use in niche applications, e.g., as materials in antifouling coatings, 14 modern soft contact lenses, 15 matrices for phase transfer reactions used in bio-and organocatalysis, and the fabrication of gas and optical sensors. 16 APCNs may also have advantages over conventional hydrogels when used as matrices for controlled drug delivery. 17 The cross-linked nature of APCNs implies some special characteristics for their microphase separation: First, chain relaxation and equilibration are slow compared to those of nonnetwork polymer systems (linear and star copolymers), and second, unavoidable loops and chain entanglements 18 lead to the entrapment of individual segments in domains of opposite philicity, compromising nanodomain purity. These explain why all experimentally studied APCNs exhibit incompletely separated nanophases with blurred interfaces, 19 in spite of theoretical studies that predict APCN phase ...

Summary Herein we report on the preparation and structural characterization of six amphiphilic polymer conetworks (APCN) based on end‐linked amphiphilic “core‐first” star block copolymers, comprising methyl methacrylate and 2‐(dimethylamino)ethyl methacrylate as the monomer repeating units in the hydrophobic and hydrophilic blocks, respectively. The various APCNs differed either in the arm composition or in the arm molecular weight. APCN synthesis was accomplished via the one‐pot, sequential group transfer polymerization (GTP) of cross‐linker, hydrophobic monomer, hydrophilic monomer, and cross‐linker again. The soluble precursors to the APCNs, i.e., the star homopolymers, the star block copolymers and the initial cross‐linker cores, were characterized in terms of their composition, size and size dispersity. The degrees of swelling in tetrahydrofuran were found to increase with the molecular weight of the arms of the stars of the APCNs, whereas the degrees of swelling in water increased with the content in hydrophilic units in the arms of the constituting stars. Small‐angle neutron scattering (SANS) indicated that most APCNs nanophase separated in D2O. The structure and size of the hydrophobic domains determined by fitting the SANS data to an appropriate model could be correlated with the molecular architecture of the APCNs. Finally, polarized light microscopy showed that all APCNs were birefringent both in water and in the dried state.

out of every cross-linking core (crosslinking node functionality) is characterized by a rather broad distribution. We also developed a variation of this method, requiring only a monofunctional initiator, in which star polymers are first prepared using either the "arm-first" or the "corefirst" strategy, followed again by the addition of cross-linker to interconnect the stars to a quasimodel network. [4] Thus, our above-described methods represent a compromise between ease of synthesis and structural control, employing a onepot sequential procedure to yield polymer networks with a good control in the elastic chain length but less control in the core functionality.In the past 20 years, we developed many quasimodel polymer network families, based on end-linked linear chains or star copolymers. In addition to purely hydrophobic and hydrophilic homopolymer systems, more complex ones were also developed, most notable of which were the amphiphilic systems, combining both hydrophobic and hydrophilic segments. [5][6][7] Amphiphilic polymer conetworks (APCNs) self-assemble in water, phase separating at the nanoscale, and yielding hydrophilic and hydrophobic domains of nanoscopic dimensions, as well as a huge interfacial area between the nano phases. These attributes endow APCNs with a great utility in a variety of applications, including uses as the material for soft contact lenses, [8] matrices for drug delivery [9] and tissue engineering, [10] and porous scaffolds for phase transfer (bio)catalysis. [11] Other complex quasimodel polymer network systems we developed include polyampholytic ones, [12,13] comprising positively and negatively ionizable polymer segments, [14,15] and double-hydrophilic ones, comprising both hydrophilic polymer segments, of which one was ionizable and the other nonionic. [16,17] Another important development within quasimodel polymer networks was the introduction of degradability, either through a degradable cross-linker [18] or through a degradable bifunctional initiator, [19] with the latter being more demanding than the former, arising from the difficulties associated with the synthesis, purification, and the stability of degradable bifunctional initiators.In the present manuscript, we report the preparation, characterization, and cleavage of degradable quasimodel poly mer networks based on interconnected "core-first" star [20] poly(methyl methacrylate)s (polyMMAs), using a degradable, Group Transfer PolymerizationSequential group transfer polymerization of cross-linker, monomer (methyl methacrylate), and cross-linker again is used to prepare cleavable polymer networks based on interconnected "core-first" star polymers. By employing a degradable and a nondegradable cross-linker, four networks are prepared. While cleavage of the degradable cross-linker residues leads to complete polymer network dissolution, the degradation products do not always display the expected molecular weight features. These products are the expected in the case of the network prepared using only the degradable cross-li...

The present study aims to investigate an odd-even effect of the number of ethylene imine units in the side-groups of totally abiotic synthetic polymers on their efficiency in DNA transfection. A library of fifteen polymers was fabricated. Two star homopolymers and one linear homopolymer based on glycidyl methacrylate were synthesized and used as precursors to which five linear oligo(ethylene imine)s (OEI) were grafted. The number of ethylene imine groups of the OEIs was varied. Specifically, ethylene diamine, diethylene triamine, triethylene tetramine, tetraethylene pentamine, and pentaethylene hexamine were used. Each of these fifteen OEI-grafted polymers was evaluated in terms of their efficiency to transfer plasmid DNA encoding firefly luciferase in C2C12 mouse myoblast cells. The transfection efficiency displayed an odd-even pattern, with all OEI-grafted polymers with an odd number of ethylene imine repeating units exhibiting higher transfection efficiency compared with those possessing an even number of ethylene imine repeating units. The odd-even effect was more pronounced for the star polymers with longer arms (degree of polymerization, DP = 100), while in case of the linear polymers, the odd-even effect was only observed for the lowest polymer loading. The cytotoxicity of the OEI-grafted polymers also followed an odd-even pattern, with the OEI-grafted star polymers with an arm DP of 100 and the linear polymers clearly presenting an odd-even effect, while the cytotoxicity of the OEI-grafted star polymers with an arm DP of 20 slightly increased with the number of ethylene imine repeating units.