Here, hydrophobic polyisobutylene and hydrophilic poly­(ethylene glycol), both of reasonably high molar masses, have been end-linked, yielding amphiphilic polymer conetwork (APCN) hydrogels that can self-organize in water into well-ordered lamellar structures. The cross-linking of hydrophobic and hydrophilic polymer segments produces networks that typically exhibit sphere-like nanodomains in water and in the bulk, but the orderly interconnection of relatively large and highly incompatible polymers leads to hydrogels that internally assemble into lamellae. This unprecedented result may be attributed to the weak force-field established by the presence of a minimal concentration of homogeneously distributed cross-links in the case of the present system, which must be contrasted to a higher concentration of randomly placed cross-linking points, which destroy long-range ordering in conventional APCN hydrogels. Significantly, the presently developed APCN hydrogels maintain good tensile mechanical properties, with their strain-at-break reaching a value of 800%. This study puts forward the design concepts for attaining highly ordered hydrogels, which would confer upon them better transport and mechanical properties and broaden their utility in biomedical and energy applications.

Polymer conetworks, which consist of two or more covalently crosslinked polymer chains, not only combine the individual characteristics of their components, but possess various unique structural features and properties as well. In this study, we report on the successful synthesis of a library of polystyrene-l-poly(dimethylsiloxane) (PSt-l-PDMS) (“l” stands for “linked by”) and polystyrene-l-poly(dimethylsiloxane)/divinylbenzene (PSt-l-PDMS/DVB) polymer conetworks. These conetworks were prepared via free radical copolymerization of styrene (St) with methacryloxypropyl-telechelic poly(dimethylsiloxane) (MA-PDMS-MA) as macromolecular crosslinker in the absence and presence of DVB with 36:1 and 5:1 St/DVB ratios (m/m), the latter leading to hypercrosslinked conetworks. Macroscopically homogeneous, transparent conetworks with high gel fractions were obtained over a wide range of PDMS contents from 30 to 80 m/m%. The composition of the conetworks determined by elemental analysis was found to be in good agreement with that obtained from the ¹H NMR spectra of the extraction residues, as a new method which can be widely used to easily determine the composition of multicomponent networks and gels. DSC, SAXS, and AFM measurements clearly indicate bicontinuous disordered nanophase separated morphology for all the investigated conetworks with domain sizes in the range of 3–30 nm, even for the hypercrosslinked PSt-l-PDMS/DVB conetworks with extremely high crosslinking density. The cocontinuous morphology is also proved by selective, composition-dependent uniform swelling in hexane for the PDMS and in 1-nitropropane for the PSt domains. The Korsmeyer–Peppas type evaluation of the swelling data indicates hindered Fickian diffusion of both solvents in the conetwork organogels. The unique nanophasic bicontinuous morphology and the selective swelling behavior of the PSt-l-PDMS and PSt-l-PDMS/DVB conetworks and their gels offer a range of various potential applications.

The glass transition temperature (T_g) is undoubtedly one of the most important characteristics of polymers, and investigating its dependence on their structure and composition is crucial from both fundamental and application points of view. This study deals with the unexpected relationship between T_g and the average molecular weight between crosslinking points (M_c) in nanophase-separated polystyrene-l-poly(dimethylsiloxane) (PSt-l-PDMS) and polystyrene-l-poly(dimethylsiloxane)/divinylbenzene (PSt-l-PDMS/DVB) polymer conetworks. In order to reveal the correlation between the T_g and M_c, a library of PSt-l-PDMS and PSt-l-PDMS/DVB conetworks was synthesized, and their compositions and T_gs were determined. Instead of the expected increase of T_g with decreasing M_c, a reverse correlation was found. Namely, the T_g decreases with decreasing M_c in these conetworks. Correlation analyses showed that the T_g linearly depends on 1/M_c, similar to the Fox–Flory relationship for homopolymers with their M_n, that is, T_g = T_g,ꝏ −K/M_c for the investigated conetworks, independent of the absence or presence of relatively low amounts of DVB as an additional small molecular weight crosslinker. This means that the PDMS macrocrosslinker acts like scissors by interrupting the mobility of the crosslinked PSt chains in the conetworks, and the T_g of the PSt segments will be close to that of PSt homopolymers with the same M_n as M_c, as found by comparison. Consistent with previous findings with other conetworks, the presence of the scissors effect of the macromolecular crosslinker in the PSt-l-PDMS and PSt-l-PDMS/DVB conetworks indicates that the scissors effect is a general phenomenon for polymer conetworks formed by crosslinking with a macromolecular crosslinker. The observed unusual T_g versus M_c relationship in the conetworks can be utilized in designing such novel materials with predetermined T_gs required for targeted applications.

The poor solubility, stability issues, and restricted bioavailability of numerous drugs and potential pharmaceutical compounds highlight the critical need for the development of polymeric nanoparticles as effective drug delivery systems. Ideal polymers for such applications must be biocompatible, provide controlled drug loading and release, and maintain the high colloidal stability of the nanoformulation. In this study, LCST-type thermoresponsive poly­(N-isopropylacrylamide)-g-(hyperbranched polyglycerol) (PNiPAAm-g-HbPG) graft copolymers, composed of two biocompatible components, were synthesized by grafting amino-monofunctional HbPG, prepared by multibranching anionic ring-opening polymerization, onto PNiPAAm chains containing succinimide active ester groups. In both aqueous solutions and phosphate-buffered saline, these graft copolymers undergo reversible aggregation and disaggregation in response to temperature changes, with linear increase of the critical solution temperature (CST) as a function of grafting density. The architecture of the copolymers enables efficient encapsulation of curcumin, a natural anticancer agent, by a simple mixing process at elevated temperatures, and the hydrophilic HbPG side chains provide excellent colloidal stability for the polymer–drug nanoformulations. Sustained release of curcumin from the PNiPAAm-g-HbPG aggregates was found, which depends on the grafting density, and the release rate can be externally triggered by decreasing the temperature. The potential biocompatibility of the PNiPAAm-g-HbPG graft copolymers was demonstrated in vitro, with no evidence of cytotoxicity or hemolytic activity against human cells. The nanoformulations of curcumin with these new graft copolymers enhanced its internalization into HT-29 human colorectal adenocarcinoma cells and significantly improved its cytostatic effect against colon cancer cells. These properties of the novel PNiPAAm-g-HbPG graft copolymers make them superior candidates for advanced drug encapsulation and delivery systems.

Here, we report, for the first time, on a new class of sulfur-containing double hydrophopbic conetworks, poly(methyl acrylate)-l-poly(3,6-dioxa-1,8-octane-dithiol-co-poly(ethylene glycol) diacrylate) (PMA-l-P(DODT-co-PEGDA). Direct one-pot synthesis of acrylate-telechelic P(DODT-co-PEGDA) macromonomer in a gram-scale for the preparation of the conetworks was obtained by copolymerization of DODT with PEGDA via simultaneous oxidative disulfide formation and thiol–ene Michael addition click reactions. Conetworks with a broad composition range of 20–70 wt% sulfur-rich P(DODT-co-PEGDA) macrocrosslinker contents were obtained by radical copolymerization. High gel fractions and composition near to that of the feed ratios verified successful conetwork synthesis. DSC analysis indicates forced blending of the immiscible PMA and P(DODT-co-PEGDA) in the conetworks by one single T_g, which deviates from both the additive rule and the Fox equation for miscible blends. These novel conetworks exhibit high thermal stability up to ~300 °C and independent decomposition patterns of the components in two separate steps. The PMA-l-P(DODT-co-PEGDA) conetworks behave as organogels by swelling in organic solvents, such as THF, acetone, toluene, with composition dependent swelling degrees up to ~900%. Degradation by breaking the disulfide bonds with thiols followed by hydrolysis with NaOH led to complete disintegration of the PMA-l-P(DODT-co-PEGDA) conetworks. These findings enable establishing a new platform for the rational design of a variety of novel sulfur-containing functional and degradable macromolecular assemblies.