Adaptive programmable materials have attracted increasing attention due to their high functionality, autonomous behavior, encapsulation, and site-specific confinement capabilities in various applications. Compared to conventional materials, adaptive programmable materials possess unique single-material architecture that can maintain, respond, and change their shapes and dimensions when they are subjected to surrounding environment changes, such as alternation in temperature, pH, and ionic strength. In this review, the most-recent advances in the design strategies of adaptive programmable materials are presented with respect to different types of architectural polymers, including stimuli-responsive polymers and shape-memory polymers. The diverse functions of these sophisticated materials and their significance in therapeutic agent delivery systems are also summarized in this review. Finally, the challenges for facile fabrication of these materials and future prospective are also discussed.

Unimolecular micelles have high functionalities, encapsulation capabilities and site specific confinement abilities in various applications.

Herein, novel conductive composite hydrogels are developed with high stretchability, ultra-softness, excellent conductivity, and good self-healing ability. The hydrogels are formed in the water/glycerol binary solvent system, in which the polyaniline nanoparticles (PANI-NPs) are incorporated into the poly(poly(ethylene glycol) methacrylate-co-acrylic acid) (P(PEG-co-AA)) scaffolds via the dynamically electrostatic interactions and hydrogen bonds. The PANI-NPs serve as conductive fillers to assign conductivity to the hydrogel, while the enhanced interfacial interactions between the PANI-NPs and P(PEG-co-AA) matrix endow the hydrogel with high stretchability (>1000%), low modulus (≈6 kPa), excellent elasticity (η = 0.07, energy loss coefficient at 500% strain), and fast self-healing ability (93.3% after 10 mins). Particularly, the desirable anti-freezing property is achieved by introducing a binary solvent system. The composite hydrogel-based sensors are proposed, with the states-independent properties, low detection limit (0.5% strain and 25 Pa), highly linear dependence, and excellent anti-fatigue performance (>1000 cycles). In addition, during the practical wearable sensing tests, various external stimulus and human motions can be detected, including speaking, writing, joint movement, or even small water droplets, indicating the potential applications for the next generation of epidermal sensors.

Poly(lactic acid) (PLA) has received increasing attention in the development of shape memory polymers (SMPs) due to its excellent physical properties and good biocompatibility. However, the intrinsically increased crystallinity of PLA at higher deformation ratios still remains a significant challenge, which remarkably restricts the chain mobility and reduces shape recovery efficiency. Being different from other types of biodegradable polymers, the diverse isomeric forms of PLA have provided great opportunities for modulation of PLA toward a favorable property by incorporating different PLA stereoisomers in one macromolecular architecture. In this paper, we report a completely amorphous PLA poly(ester urethane) elastomer that exhibits excellent shape fixity (>99%) and shape recovery (>99%) in a time frame of seconds. By means of adjusting the stereoisomeric ratios and control over architecture, the resultant poly(PLLA/PDLLA urethane)s (PLDU) elastomers show a single glass transition temperature (T g ), as the only thermal event, in the range of 38−46 °C in a predictable manner. The elastic moduli of PLDU elastomers display a 100-fold loss during the sharp transition from a glassy to a rubbery state with temperature alternation across their corresponding T g , indicating a successful manipulation of the thermo-mechanical properties by temperature as required in thermally induced SMPs. In addition, all samples display a typical elastomeric behavior with elongation at break (ε b ) greater than 400%. The effect of the stereoisomer content on the tensile modulus and elastic mechanical behavior were also systematically investigated. Together with the prominent degradation property, the new PLDU elastomers developed in this study show great potential for biomedical applications as shape memory implants.

Macrocyclic molecular brushes c‐PHEMA‐g‐(PS‐b‐PEO) consisting of macrocyclic poly(2‐hydroxylethyl methacrylate) (c‐PHEMA) as backbone and polystyrene‐b‐poly(ethylene oxide) (PS‐b‐PEO) amphiphilic block copolymers as side chains were synthesized by the combination of atom transfer radical polymerization (ATRP), click chemistry, and single‐electron transfer nitroxide radical coupling (SET‐NRC). First, a linear α‐alkyne‐ω‐azido heterodifunctional PHEMA (l‐HCC‐PHEMA‐N3) was prepared by ATRP of HEMA using 3‐(trimethylsilyl)propargyl 2‐bromoisobutyrate as initiator, and then chlorine end groups were transformed to N3 group by nucleophilic substitution reaction in DMF in the presence of an excess of NaN3. The 3‐trimethylsilyl groups could be removed in the presence of tetrabutylammonium fluoride, and the product was cyclized by “click” chemistry in high dilution conditions. The hydroxyl groups on c‐PHEMA were transferred into bromine groups by esterification with 2‐bromoisobutyryl bromide and then initiate the ATRP of styrene. The formed macrocyclic molecular brushes c‐PHEMA‐g‐PS were coupled with the TEMPO‐PEO to afford the target macrocyclic molecular brushes c‐PHEMA‐g‐(PS‐b‐PEO) by SET‐NRC, and the efficiency is as high as 80∼85%. All of the intermediates and final product were characterized with 1H NMR, Fourier transform infrared (FTIR), and gel permeation chromatography in details © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011

An amphiphilic heteroeight-shaped polymer cyclic-[poly­(ethylene oxide)-b-polystyrene]2 ([c-(PEO-b-PS)]2) composed of hydrophilic PEO and hydrophobic PS blocks was synthesized by combination of “click” chemistry with anionic ring-opening polymerization (ROP) and atom transfer radical polymerization (ATRP) mechanisms. According to “core-first” strategy, the A2B2 star-shaped precursor (PEO-alkyne)2-(PS-N3)2 was obtained by successive ROP of EO monomer, ATRP of St monomer, and modification of functional groups. Under high dilution condition, the intramolecular cyclization of (PEO-alkyne)2-(PS-N3)2 by “click” chemistry produced the amphiphilic heteroeight-shaped polymer [c-(PEO-b-PS)]2. The target copolymers and intermediates were well characterized by GPC, MALDI-TOF MS, 1H NMR, and FT-IR. The self-assembly behavior of [c-(PEO-b-PS)]2 and its precursor of (PEO-alkyne)2-(PS-N3)2 were investigated and compared by transmission electron microscopy (TEM) and dynamic light scattering (DLS). In both cases, the spherical micelles were observed, however, the size of formed micelles increased from a star-shaped to a cyclic topology.

A simple and effective synthesis strategy is developed for electroactive β-PVDF-hfp where both intermolecular interaction and arrangement of surface functional groups operate.

To meet various practical requirements and enhance human experience, hydrogels possessing multifunctionality are of great significance for flexible wearable sensors. Herein, a novel strategy has been developed to fabricate nanocomposite hydrogels with a combination of excellent stretchability, rapid recoverability, self-healing, and outstanding adhesiveness. The PAAc/SiO2-g-PAAm nanocomposite hydrogels were facilely prepared through the polymerization of acrylic acid (AAc) using SiO2-g-polyacrylamide core–shell hybrid nanoparticles (SiO2-g-PAAm) as the dynamic cross-linking center. The densely dynamic hydrogen bonds between PAAc matrices and grafted PAAm chains could reversibly be destructed and reconstructed to dissipate a large amount of energy. Due to this unique feature, the formulated hydrogels showed a wide spectrum of desirable properties, including skin-mimetic modulus, excellent stretchability (1600%), exceptional self-healing properties (96.5% at ambient temperature), and fast recoverability. The sensors fabricated with the prepared hydrogels exhibited a high detection sensitivity in the strain range from 50% to 500% with a gauge factor value of 5.86, rapid response time, and good antifatigue performance. Depending on the outstanding adhesiveness, this sensor could attach to different substrates to release the real-time motion monitoring. In the practical wearable sensing test, various human motions, including tiny-scaled swallowing, laughing, and speaking, as well as large-scaled wrist, elbow, and knee movements during basketball shooting, could be sensed. These demonstrations heralded the potential application of our sensor in accurate and long-term human motion monitoring.