Defect Crystal Formation and Thermal-Induced Structural Ordering of Semicrystalline Copolymers Induced by Comonomer Inclusion/Exclusion.

Comonomer defects can induce semicrystalline polymers to form unique crystalline structures (., defect crystals), which can greatly influence the materials' physical properties. However, the formation mechanism and structural evolution of defect polymer crystals are not yet well understood.

Spatially and Temporally Programmable Transparency Evolutions in Hydrogels Enabled by Metal Coordination toward Transient Anticounterfeiting.

Hydrogels have emerged as promising candidates for anticounterfeiting materials, owing to their unique stimulus-responsive capabilities. To improve the security of encrypted information, efforts are devoted to constructing transient anticounterfeiting hydrogels with a dynamic information display. However, current studies to design such hydrogel materials inevitably include sophisticated chemistry, complex preparation processes, and particular experimental setups.

Linearly-Changed Thermal Behavior and Depressed Brill Transition in Long-Chain Polyamides Substituted by Methyl Side Groups.

Side substitution is an effective way of functionalizing and modifying the properties of polyamides. Meanwhile, side substitution would significantly influence the crystallization kinetics and polymorphic phase transition of polyamides, which, however, has not been well elucidated. Herein, we synthesized the side-substituted long-chain polyamides with various content of methyl pendent groups and investigated their crystallization and phase transition behaviors.

Ultrasensitive Ionic Conductors with Tunable Resistance Switching Temperature Enabled by Phase Transformation of Polymer Cocrystals.

Phase-transformable ionic conductors (PTICs) show significant prospects for functional applications due to their reversible resistance switching property. However, the representative design principle of PTICs is utilizing the melt-crystallization transition of ionic liquids, and the resistance switching temperatures of such PTICs cannot be tuned as desired. Herein, a new strategy is proposed to design PTICs with on-demand resistance switching temperatures by using the melt-crystallization transition of polymer cocrystal phase, whose melting temperature shows a linear relationship with the polymer compositions.

Crystal Polymorphism of Isodimorphic Polyesters Tuned by - and -C═C Comonomer Units.

Polymorphism is ubiquitous in polymer crystallization due to the diversified chain conformations and interchain packings in polymer crystals. Controlling chain conformation is effective in tailoring the crystal polymorphism of polymers, which, however, is challenging at the molecular level. Herein, we have synthesized poly(butylene adipate) (PBA)-based copolymers containing C═C units and demonstrated the important role of /-C═C units in tuning the chain conformation and crystal polymorphism of polymers.

Tunable Crystallization Kinetics and Crystal Polymorphism in Semicrystalline Polymers: Insight into the Multilevel Structural Order of Polymer Melts.

The melting of semicrystalline polymers is a typical multistep process and involves a series of intermediate melt states. However, the structural characteristics of the intermediate polymer melt is unclear. Herein, we choose polymorphic -1,4-polyisoprene (PI) as a model polymer system and elucidate the structures of the intermediate polymer melt and their strong effects on the following crystallization process.

Multi-Level Information Encryption/Decryption of Fluorescent Hydrogels Based on Spatially Programmed Crystal Phases.

The growing urgence of information protection promotes continuously the development of information-encryption technique. To date, hydrogels have become an emerging candidate for advanced information-encryption materials, because of their unique stimulus responsiveness. However, current methods to design multi-level information-encrypted hydrogels usually need sophisticated chemistry or experimental setup.

Light-Induced Crystalline Size Heterogeneity of Polymers Enables Programmable Writing, Morphing, and Mechanical Performance Designing.

Constructing the spatio-selective crystalline structures has been an effective strategy to diversify the functions and applications of polymers. However, it is still challenging to program the crystalline heterogeneity into commercialized polymers and realize associate functions by a simple yet generalizable method. Herein, we propose a facile approach to fabricate multifunctional materials by programming the spatial distribution of crystal size in semicrystalline polymers.

Role of Chain Entanglements in the Stereocomplex Crystallization between Poly(lactic acid) Enantiomers.

Stereocomplex (SC) crystallization between polymer enantiomers has opened a promising avenue for preparing high-performance materials. However, high-crystallinity SCs are difficult to achieve for high-molecular-weight (HMW) enantiomeric blends of chiral polymers [e.g.

Self-evolving materials based on metastable-to-stable crystal transition of a polymorphic polyolefin.

Living organisms can self-evolve with time in order to adapt to the natural environment. Analogically, self-evolving materials also show similar properties based on non-equilibrium structural transformation. The common design of these materials tends to rely on solutions and hydrogels, yet only little attention has been paid to dry materials.

Polymorphic Phase Formation of Liquid Crystals Distributed in Semicrystalline Polymers: An Indicator of Interlamellar and Interspherulitic Segregation.

Amorphous and melted components can segregate into the interlamellar or interspherulitic regions of polymer crystals in their blends/mixtures; this phase behavior strongly influences the physical properties and functions of materials. However, it is experimentally difficult to evaluate the spatial distributions of the other components in polymer crystals. Herein, we use a small-molecule liquid crystal (LC) as a probe and find that it forms different solid phases when mixed with the semicrystalline polymer poly(l-lactic acid) (PLLA).

Stress-Free Two-Way Shape Memory Effects of Semicrystalline Polymer Networks Enhanced by Self-Nucleated Crystallization.

Stress-free two-way shape memory polymers (2W-SMPs) capable of reversible shifting between two distinct shapes are versatile platforms for the development of future smart devices. However, it is challenging to prepare stress-free 2W-SMPs with good actuation performance and shape programmability from single-component semicrystalline polymers. Herein, we demonstrate a straightforward and universal strategy for preparing 2W-SMPs through self-nucleated crystallization (SNC) of semicrystalline polymers.

Expansion Properties and Diffusion of Blowing Agent for Vinylidene Chloride Copolymer Thermally Expandable Microspheres.

Vinylidene chloride copolymer microspheres were synthesized by in situ suspension copolymerization of vinylidene chloride (VDC), methyl methacrylate (MMA), and/or acrylonitrile (AN) in the presence of a paraffin blowing agent. The effects of shell polymer properties including compositions, glass transition temperature (), crosslinking degree, blowing agent type, and encapsulation ratio () on the expansion properties of copolymer microspheres were investigated. Moreover, the diffusion properties of blowing agent in copolymer microspheres were studied.

Stereocomplexed and homocrystalline thermo-responsive physical hydrogels with a tunable network structure and thermo-responsiveness.

The widespread application of thermo-responsive hydrogels requires materials with robust mechanical properties and tunable responsiveness. Herein, we report robust thermo-responsive physical hydrogels with a tunable network structure and responsiveness by controlling the manner of crystallization of hydrophobic blocks. Biocompatible, stereocomplexable poly(l-lactic acid) (PLLA) and poly(d-lactic acid) (PDLA) were introduced into thermo-responsive poly(N-isopropylacrylamide) (PNIPAM) to obtain the enantiomeric grafted copolymers PNIPAM-g-PLLA and PNIPAM-g-PDLA and their corresponding hydrogels.

Programmable Reversible Shape Transformation of Hydrogels Based on Transient Structural Anisotropy.

Stimuli-responsive shape-transforming hydrogels have shown great potential toward various engineering applications including soft robotics and microfluidics. Despite significant progress in designing hydrogels with ever more sophisticated shape-morphing behaviors, an ultimate goal yet to be fulfilled is programmable reversible shape transformation. It is reported here that transient structural anisotropy can be programmed into copolymer hydrogels of N-isopropylacrylamide and stearyl acrylate.

Sequence-Rearranged Cocrystalline Polymer Network with Shape Reconfigurability and Tunable Switching Temperature.

Switching temperature () is a key parameter governing the service condition of shape memory polymers (SMPs). However, tuning of SMPs often requires sophisticated synthesis or intricate processing. Herein, we report a simple yet effective strategy to prepare the SMPs with tunable and good reconfigurability by using the cocrystalline polyesters as the reversible phase.

Thermoresponsivity, Micelle Structure, and Thermal-Induced Structural Transition of an Amphiphilic Block Copolymer Tuned by Terminal Multiple H-Bonding Units.

Constructing noncovalent interactions has been a benign method to tune the stimuli responsivity and assembled structure of polymers in solution; this is essential for controlling the functions and properties of stimuli-responsive materials. Herein, we demonstrate a novel supramolecular strategy to manipulate the cloud point () and assembled structure of thermoresponsive polymers in solution by using H-bonding interactions. We use poly(lactide--glycolide)--poly(ethylene glycol)-- poly(lactide--glycolide) (PLGA-PEG-PLGA) as a model thermoresponsive polymer and functionalize its chain terminals by the self-complementary quadruple H-bonding motif, 2-ureido-4[1]-pyrimidinone (UPy).

Tuning the Thermoresponsivity of Amphiphilic Copolymers via Stereocomplex Crystallization of Hydrophobic Blocks.

Thermoresponsive polymers that exhibit a cloud point temperature () are an important class of stimuli-responsive polymers that have great potential for biomedical applications. Precise tuning of the is of fundamental importance for designing thermoresponsive polymers. However, tuning the generally requires sophisticated control over the chemical and assembled structures of thermoresponsive polymers.

Polymorphic Crystal Transition and Lamellae Structural Evolution of Poly( p-dioxanone) Induced by Annealing and Stretching.

Semicrystalline polymers usually undergo multilevel microstructural evolutions under high-temperature annealing and stretching deformation; this is essential to tailor the physical properties of polymer products in industrial processing. Here, we choose poly( p-dioxanone) (PPDO), a typical biodegradable, biocompatible, and bioresorbable polymer, as a model semicrystalline polymer and investigated its polymorphic structural transition and crystalline lamellar evolution under high-temperature annealing and stretching. High-temperature annealing caused the α'-to-α phase transition of PPDO, accompanied by the improvement of crystallinity ( X) and thickening of crystalline lamellae.

Stereocomplexed and Homochiral Polyurethane Elastomers with Tunable Crystallizability and Multishape Memory Effects.

Design of the polymer networks with tunable mechanical properties and multishape memory effects (multi-SMEs) is highly desired in the engineering applications. Herein, we report on the stereocomplexed and homochiral polyurethane (PU) elastomers with tunable multi-SMEs by cross-linking the triblock prepolymers bearing the poly(l-lactic acid) (PLLA) and poly(d-lactic acid) (PDLA) enantiomeric segments. The homochiral PU is nearly amorphous, yet the stereocomplexed PU becomes highly crystalline due to the stereocomplexation of enantiomeric segments.

Dual-Crosslink Physical Hydrogels with High Toughness Based on Synergistic Hydrogen Bonding and Hydrophobic Interactions.

Constructing dual or multiple noncovalent crosslinks is highly effective to improve the mechanical and stimuli-responsive properties of supramolecular physical hydrogels, due to the synergistic effects of different noncovalent bonds. Herein, a series of tough physical hydrogels are prepared by solution casting and subsequently swelling the films of poly(ureidopyrimidone methacrylate-co-stearyl acrylate-co-acrylic acid). The hydrophobic interactions between crystallizable alkyl chains and the quadruple hydrogen bonds between ureidopyrimidone (UPy) motifs serve as the dual crosslinks of hydrogels.

Stereocomplexed physical hydrogels with high strength and tunable crystallizability.

Physical hydrogels crosslinked by non-covalent interactions have attained increasing attention due to their good mechanical properties and processability. However, the use of feasible and controllable non-covalent interactions is highly essential for preparing such hydrogels. In this article, we report on stereocomplexed physical hydrogels prepared by simple casting and swelling of amphiphilic graft copolymers bearing a poly(acrylic acid) (PAA) backbone and poly(l-lactic acid) (PLLA) or poly(d-lactic acid) (PDLA) stereocomplexable side chains.

A facile self-templating synthesis of carbon frameworks with tailored hierarchical porosity for enhanced energy storage performance.

Herein, we present a facile synthesis of hierarchical carbon frameworks with microporous skeletons and interconnected meso/macropores by employing poly(vinylidene chloride-co-methyl acrylate)-b-polystyrene copolymers as precursors. The obtained porosity can be tuned over a broad range via well-selected block proportions of the precursor, enabling its advantageous applications in target-oriented energy storage systems.

Polymorphic Crystallization and Crystalline Reorganization of Poly(l-lactic acid)/Poly(d-lactic acid) Racemic Mixture Influenced by Blending with Poly(vinylidene fluoride).

The effects of poly(vinylidene fluoride) (PVDF) on the crystallization kinetics, competing formations of homocrystallites (HCs) and stereocomplexes (SCs), polymorphic crystalline structure, and HC-to-SC crystalline reorganization of the poly(l-lactic acid)/poly(d-lactic acid) (PLLA/PDLA) racemic mixture were investigated. Even though the PLLA/PDLA/PVDF blends are immiscible, blending with PVDF enhances the crystallization rate and SC formation of PLLA/PDLA components at different temperatures that are higher or lower than the melting temperature of the PVDF component; it also facilitates the HC-to-SC melt reorganization upon heating. The crystallization rate and degree of SC crystallinity (Xc,SC) of PLLA/PDLA components in nonisothermal crystallization increase after immiscible blending with PVDF.

Thermoresponsive physical hydrogels of poly(lactic acid)/poly(ethylene glycol) stereoblock copolymers tuned by stereostructure and hydrophobic block sequence.

CBABC-type poly(lactic acid) (PLA)/poly(ethylene glycol) (PEG) pentablock copolymers composed of a central PEG block (A) and enantiomeric poly(l-lactic acid) (PLLA, B), poly(d-lactic acid) (PDLA, C) blocks were synthesized. Such pentablock copolymers form physical hydrogels at high concentrations in an aqueous solution, which stem from the aggregation and physical bridging of copolymer micelles. These gels are thermoresponsive and turn into sols upon heating.