Hard Segment Domains Research Articles

Understanding the shape-memory mechanism of thermoplastic polyurethane by investigating the phase-separated morphology: A dissipative particle dynamics study

Shape-memory polyurethanes (SMPUs) are promising materials that change shape in response to external heat. These polymers have a dual-segment structure: a hard segment for netpoint and a soft segment for molecular switch. Understanding the molecular behavior of each segment and microphase-separated morphology is crucial for comprehending the shape-memory mechanism. This study aimed to understand the shape-memory behavior by observing the phase separation of SMPU using mesoscale models based on dissipative particle dynamics (DPD) simulations. The SMPU copolymer was modeled using 4,4′-diphenylmethane diisocyanate (MDI, hard segment) and poly(ethylene oxide) (PEO, soft segment). By calculating segment solubility and repulsion parameters, we found that the hard-segment domain changes from isolated form to a lamellar and interconnected structure and eventually to a continuous form as its content increases. Combining these insights with shape-memory performance models can enhance our understanding of better SMPU design and contribute significantly to the optimization of smart stimuli-responsive materials.

Shock Hugoniot Calculations of Newly Designed Thermoplastic Elastomers and Comparison with Classical Binder Estane.

Our purpose is to design excellent binder candidates used in polymer-bonded explosives (PBX) according to the calculated shock of Hugoniot. Here, we mainly examined the thermoplastic elastomer (TPE) binders commonly used in PBX formulations. Equilibrium molecular dynamics (MD) simulation and mixing rule methods were used to calculate the shock Hugoniot values of 180 newly designed TPEs. We focused on the influence of the polymerization degree, contents, and types of soft and hard segments composed of TPEs on the shock Hugoniot and compared them with the classic PBX binder, Estane. The results show that the hard segment has an effect on the Hugoniot curve, which gradually diminishes as the degree of polymerization increases. The underlying physical mechanism can be attributed to the presence of a large number of hydrogen bonds in hard segment domains. The shock Hugoniot of TPEs also depends on the type of soft segments. The volume compression rate of TPEs decreases with increasing content of hard segments under a given shock. By comparing with Estane, a TPE binder commonly used in PBX, we ultimately chose several new TPEs with the potential to serve as PBX binders in terms of shock performance.

The strengthening mechanism of mechanical performance for polyurethanes with micro-content crosslinkers

Chemical crosslinking is one widely used method to endow polyurethane (PU) with desirable properties. However, the introduction of crosslinkers in PU elastomers can often lead to the destruction of phase separation, resulting in weakened mechanical properties. Herein, a series of PUs with micro-content crosslinker were synthesized from poly(oxytetramethylene) glycol (PTMG), diphenylmethane-4,4′-diisocyanate (MDI), and chain extender of butane-1,4-diol (BDO) containing varied amounts of glycerol. The phase separation of PUs decreases with increased glycerol content, while the tensile strength increases. To elucidate this enhancement in mechanical properties, morphology investigation with capability of direct observation of components distribution is employed. An increased thickness of interphase between the domain of hard segment (HS) and soft segment (SS) is observed, which indicates that more HS is moved to the interphase upon the introduction of glycerol. The results of electron energy loss spectroscopy (EELS) further disclosed that glycerol formed aggregations located at the interphase. These aggregations increase the crosslinking density of the interphase, which strengthens HS domains and prevents them from being destroyed under tension, thereby increasing the tensile strength. It is the first time of disclosing distribution feature of micro-content crosslinker of PU as well its strengthening mechanism in tensile strength, which could assist in developing PU with desirable mechanical properties.

Effect of Geometrical Confinement on Ordering of Thermoplastic Polyurethanes with Crystallizable Hard and Soft Blocks

A series of multi-block thermoplastic polyurethanes incorporating different soft block structures was synthesized. This was achieved using a poly(butylene adipate) oligomer combined with its macrodiols of both an aromatic and aliphatic nature. The composition of the hard block included 1,6-hexamethylene diisocyanate, 4,4′-diphenylmethane diisocyanate, and 1,4-butanediol. For the first time, the structural evolution and phase composition of both the hard and soft segments were analyzed during in situ thermal treatments. A combination of synchrotron small- and wide-angle X-ray scattering, differential scanning calorimetry, thermogravimetric analysis, and Fourier transform infrared spectroscopy was used to determine the influence of the macrodiol’s nature and crystallization conditions on the polymorphic behavior of poly(butylene adipate). Using a new synthesis scheme, a relatively high degree of crystallinity for urethane blocks was achieved, which depended on the diisocyanate type in the structure of the soft segment. The hard segment domains imposed geometrical constraints on poly(butylene adipate), thereby altering its crystallization process compared to the neat oligomer. Thus, crystallization after annealing at a low temperature (80 °C) was fast, predominantly yielding a metastable β-phase. When heated to 180 °C, which was higher than the hard segment’s melting temperature, a phase-separated structure was observed. Subsequent crystallization was slower, favoring the formation of the stable α-PBA modification. The phase separation could be observed even after the hard block melting. Notably slow crystallization from an isotropic melt was documented after the disruption of phase separation at 230 °C.

Antiswelling and robust supramolecular polyurea hydrogels induced by the synergy of hydrogen bond and hydrophobic interaction for constructing durable underwater anti‐oil‐fouling coatings

AbstractHydrogels are attractive materials for constructing underwater antifouling coatings on solid substrates. However, the application of hydrogel coatings usually faces the obstacles of complex preparation process and poor durability. Herein, we present a facile method to prepare durable hydrogel coatings on metal foils based on rationally designed supramolecular polyurea (PU) hydrogels. PU hydrogels are designed to be cross‐linked with hydrogen bonds (H‐bonds) and hydrophobic interactions in the hard segment domains by using dihydrazides with different alkyl spacer lengths ((CH2)m) as chain extender. The synergy of H‐bond and hydrophobic interaction can stabilize H‐bonds in water, as confirmed by Raman spectroscopy. As a result, PU hydrogels exhibit antiswelling capacity and robustness in both deionized water and seawater. Subsequently, PU hydrogel coatings on Cu/Al foils are prepared by convenient brush coating and subsequent swelling. The resulting hydrogel coatings exhibit excellent underwater anti‐oil‐adhesion and self‐cleaning property, and are durable enough to withstand various static and dynamic damaging tests. The good durability of PU hydrogel coatings should be ascribed to the robust adhesion interface and excellent antiswelling capacity of PU hydrogels. The combination of facile preparation and good durability makes PU hydrogel coatings promising candidates for reliable underwater antifouling.

Quantification Characterization of Hierarchical Structure of Polyurethane by Advanced AFM and X-ray Techniques.

Polyurethane (PU) with microphase separation has garnered significant attention due to its highly designable molecular structure and a wide range of adjustable properties. However, there is currently a lack of systematic approaches for quantifying PU's microphase separation. To address this research gap, we utilized an atomic force microscopy (AFM) nanomechanical mapping technique along with Gaussian fitting to recolor and quantitatively analyze the evolution of PU's microphase separation. By varying the ratios of the chain extender to cross-linking agent, we observed the changes in the hydrogen bonding between the soft and hard segments. As the ratio of the chain extender to cross-linking agent decreases, the strength of the hydrogen bonding weakens, resulting in a reduction in the quantity and phase percentage of hard segment (HS) domains. Consequently, the degree of microphase separation between the soft and hard segments decreases, leading to specific alterations in the material's mechanical properties and dynamic viscoelasticity. To further investigate the hierarchical structure of PU, we employed various techniques, such as X-ray analysis, transmission electron microscopy (TEM), and AFM-based infrared spectroscopy (AFM-IR). Our findings reveal a spherulite pattern composed of lamellae within the HS domains, with the cross-linking density gradually increasing from the center to the periphery. Overall, our comprehensive characterization of PU provides valuable insights into its hierarchical structure and establishes a quantitative framework to explore the intricate relationship between the structure and properties.

Partial crystalline organosilicon-based polysiloxane-polyurethane copolymers

Partial crystalline polysiloxane-based polyurethane copolymers were prepared by using hydroxyethoxypropyl capped polydimethylsiloxane (PDMS) as soft segment and α,ω-(bis (hydroxyethylthioether) ethyl)-disiloxane as chain extender. Due to this partial crystalline structure, the copolymer shows fairly good tensile properties and multiple shape deformation property. Repeated tensile tests revealed that stretch led to crystal destruction, and the microstructure of samples became stable after twice stretches. The lost crystallinity got 85.1% recovered upon treated at 60 °C for 1 h. It was proved that partial crystallization properties of the polysiloxane-polyurethane copolymer were from combined effects of polysiloxane soft segment and disiloxane chain extender. This unique crystallization kinetics of -(Si-O-Si)x- structure coexisting in soft and hard segments is regarded as one main reason to form crystalline hard segment domains in a common two-step synthesis.

Improving the Mechanical Properties and Tribological Behavior of Sulfobetaine Polyurethane Based on Hydrophobic Chains to Be Applied as Artificial Meniscus.

In the context of meniscus reconstruction in knee joints, current bulk biomaterials fail to meet the clinical demands for both excellent mechanical strength and low coefficient of friction. In this research, zwitterionic polyurethanes (PUs) with varying sulfobetaine (SB) groups were synthesized as the potential materials for artificial meniscus to investigate the relationship between the structures of SB groups and the performances of PUs. Under the saturation condition of 3 mg/mL hyaluronic acid aqueous solution, PU with long-alkyl chains and SB groups (PU-hSB4) exhibited a good tensile modulus (111.5 MPa) because the hydrophobic interaction of carbon chains was able to maintain the ordered aggregations of hard segment domains. Interestingly, hydrophobic chains in the molecular chain could also improve the tribological performance of PU-hSB4 instead of resulting from the surface roughness of samples, the components of lubricants, and the counterface of samples. A thicker and relatively stable hydration layer of noncrystal water was formed on the surface of PU-hSB4, which exhibited superior resistance to external forces compared to other PUs. Even if the hydration layer was damaged, PU-hSB4 was able to resist the compression of cartilage due to its high surface modulus, thus maintaining a similar and stable coefficient of friction (0.15-0.16) to native meniscus (0.18) and excellent wear resistance. In addition, the low cytotoxicity of PU-hSB4 further demonstrated its great potential to be applied in artificial meniscus instead.

Imparting Reprocessability, Quadruple Shape Memory, Self-Healing, and Vibration Damping Characteristics to a Thermosetting Poly(urethane-urea)

The advent of dynamic covalent bond chemistry (DCBC) has sparked renewed research interest in reprocessability of thermosetting polymers. However, combining reprocessability with stimuli-responsiveness remains a challenge for futuristic applications. Usually, a combination of complementary DCBCs is employed to integrate reprocessability with shape memory as well as self-healing (SH) attributes in a single polymeric system. In the present work, we report two-component poly(urethane-urea) (PUU) networks, with varied hard segment (HS) concentrations, that exhibit quadruple shape memory (QSM), efficacious vibration damping, thermally activated intrinsic SH as well as multiple cycles of thermal reprocessability. The component A is an isocyanate capped bi-soft segment blend of polybutadiene diol and polypropylene glycol, while the second component comprises an aromatic diamine chain extender solubilized in an oligomeric polyoxypropylene triol. The networks characterized through FTIR as well as small- and wide-angle X-ray scattering (SAXS and WAXD) revealed a phase-separated morphology with extensive hydrogen-bonding (H-bonding) interactions in the HS domains of the PUU networks. Dynamic mechanical analysis (DMA) measurements revealed broad dissipation factor (tan δ) vs temperature and frequency profiles of the networks, which could be leveraged for efficacious passive vibration damping applications. A dissociative mechanism of urethane and urea bond exchange, evidenced from temperature-dependent FTIR studies enabling facile stress relaxation, is proposed to be the mechanistic origin of the reprocessability and SH of the networks. A broad dissipation factor (tan δ) vs temperature profiles endowed the networks with QSM characteristics. We posit that the study is relevant for expanding the scope of DCBCs for development of reprocessable thermosetting polyurethanes with multiple smart functionalities.

Self-Healable, Recyclable, and Reprocessable Poly(urethane–urea) Elastomers with Tunable Mechanical Properties Constructed by Incorporating Triple Dynamic Bonds

Elastomers that are self-healable, recyclable, reprocessable, and customizable in mechanical properties are desired for numerous industries but remain challenging to achieve. Herein, we develop novel poly(urethane–urea) (PUU) elastomers involving triple dynamic bonds in a convenient and efficient manner. Briefly, a prepolymer based on polyetheramine terminated by asymmetric alicyclic diisocyanate was synthesized and chain-extended with two diamines to generate a PUU elastomer containing dynamic hydrogen bonds (H bonds) and disulfide bonds, followed by incorporation with Zn2+ ions for Zn2+–urea coordination. The coordination bonds were proved to augment the microphase separation leading the hard segment domains to be homogeneously distributed in the soft phase and serve as nanoscale reinforcements for the simultaneous improvement of the mechanical modulus, strength, and toughness, which were facilely tunable by varying the zinc content. In the meantime, self-healing could be achieved at room temperature or no higher than 40 °C owing to the dynamic exchangeable bonds. Impressively, the elastomers can be reprocessed by hot pressing and recycled by solvent dissolution. This work, combining the macromolecular structure design with metal–urea coordination bonds, adds a new strategy to the toolbox of constructing elastomers with tunable and advanced performances.

Enhanced foaming ability of thermoplastic polyurethane by crystallization during mold-opening foam injection molding with supercritical N2 as blowing agents

This study provides an insight into the foaming of thermoplastic polyurethane (TPU), which was improved by the crystallization of hard segment domains. This study investigated the effects of packing time in the mold-opening foam injection molding (MOFIM) technology on the crystallization behavior of hard segments in TPU and the cell morphology of TPU foams. It was observed that the prolongation of the packing time, corresponding to a longer crystallization time before foaming, induced an increased crystallinity in the injection-molded TPU solids and foams due to the crystals becoming more close-packed. The enhancement of the foamability of TPU was attributed not only to the increased crystallinity of hard segments, but also to the broader distribution of crystals at the same crystallinity. Furthermore, TPU foams with greater hardness have smaller cell size, higher cell density, and narrower distribution in cell size owing to their higher viscosity and storage modulus than those with lower hardness prepared under the same conditions.

A facile method to fabricate supramolecular polyurea hydrogel coated mesh with long-term stable underwater superoleophobicity for oil/water separation

Hydrogel is an ideal coating material to fabricate superhydrophilic and underwater superoleophobic filtration membrane used for oil/water separation. However, it remains challenging to fabricate hydrogel coated mesh with long-term stable underwater superoleophobicity by a facile method. Herein, we present a facile method to fabricate supramolecular polyurea (PU) hydrogel coated mesh that can maintain stable underwater superoleophobicity. PU hydrogels were obtained by swelling phase separated PU film in water till equilibrium, and thus PU hydrogel coatings can be prepared via simple brushing operation. PU hydrogels were rationally designed to be crosslinked by sextuple H-bonds within hard-segment domains, so as to obtain excellent anti-swelling capacity and robustness in deionized water, artificial seawater, and acidic/alkaline (pH = 0–11) environments. The corresponding PU hydrogel coated meshes exhibited anti-fouling capability and underwater superoleophobicity. Moreover, PU hydrogel coated meshes can endure corrosive environments, long-term immersion and mechanical abrasion to maintain stable underwater superoleophobicity. Consequently, they can demonstrate high oil/water separation efficiency (>99 %) in harsh environments and stable reusability upon long-term immersion (3 weeks). The PU hydrogel coated mesh show great potential for practical oily wastewater treatment.

An insight on the effect of the hard segment domain on the thermo‐mechanical and surface properties of new piperazine‐based polyurethanes

Abstract1,4‐piperazinediethanol was used as chain extender in the synthesis of new polyurethanes based on poly (tetramethylene oxide) glycol and 1,6‐hexamethylene diisocyanate. Also new polyurethanes which contain renewable cross‐linkers (polyethylene glycol sorbitan monolaurate (Tween® 20) and sorbitan monolaurate (Span® 20)) were obtained. The degree of microphase separation and the weight fraction of hydrogen‐bonded urethane groups is calculated by FTIR spectroscopy. The thermal, mechanical, and surface properties are examined and related with the structure of the corresponding polyurethanes. Linear polyurethanes have good thermal stability with the 5% weight loss in the range 250–280°C and cross‐linked samples in the range 295–320°C. Tensile strength and elongation at break have higher values (38 MPa and 1140%) when the 1,4‐piperazinediethanol content is lower. The increase in the piperazine content leads to more hydrophilic polyurethane surface. Cross‐linkers increase the water contact angle and thus the surface of the corresponding polyurethanes becomes hydrophobic.

High-Strength Heat-Elongated Thermoplastic Polyurethane Elastomer Consisting of a Stacked Domain Structure.

We found that a high-strength elastomer was obtained by the heat elongation of a thermoplastic polyurethane (TPU) film consisting of a high content of crystalline hard segments (HS). The stress upturn continuously increased with the elongation ratio without a decrease in the strain recovery by heat elongation, i.e., the stress at break of a quenched TPU film was increased from 55 to 136 MPa by heat elongation at an elongation ratio of 300%. The results of small-angle X-ray scattering, DSC, and AFM observations revealed that: (1) anisotropically shaped HS domains were stacked at a nanometer scale and the longer direction of the HS domains was arranged perpendicular to the elongated direction due to the heat elongation, (2) the densification of the HS domains increased with increases in the elongation ratio without a significant increase in the crystallinity, and (3) the stacked domain structure remained during the stretching at 23 °C. Thus, the strengthening of the elongated TPU might be attributed to the densification of the HS domains in the stacked structure, which prevents the fracture of the HS domains during the stretching.

Highly efficient self-healable and robust fluorinated polyurethane elastomer for wearable electronics

• The polyurethane elastomers with multiple functions were successfully prepared. • The polyurethane elastomer has excellent self-healing properties and mechanical robustness. • Fluorinated polyurethane elastomers can be used to construct wearable electronic devices. Self-healable polyurethanes (PUs) containing reversible dynamic bonds have been widely recognized and rapidly developed in recent years. Because the self-heal capability and mechanical properties of materials are mutually exclusive in nature, it is still a formidable challenge to design a highly efficient self-healable and robust PUs, especially in wearable electronics field. Herein, a series of self-healable thermosetting PU elastomer based on widely used phenolic urethane bond was prepared to achieve above requirements. In order to investigate the effect of introducing different bisphenol chain extenders into the hard segment domain on the dissociation temperature of phenolic carbamate bond, both bisphenol A (BPA) and bisphenol AF (BPAF) were used to synthesize thermosetting PU elastomers (PU-BPA and PU-BPAF). The healing efficiency of PU-BPA was 95% with a thermal treatment at 100 °C for 1 h, and its initial dissociation temperature was 90 °C. Due to the presence of trifluoromethyl (-CF 3 ) group, the thermal self-healing efficiency of PU-BPAF was improved, which could be completely healed (100%) at the same conditions and its initial dissociation temperature was reduced to 80 °C. PU-BPAF were used to prepare a self-healable triboelectric nanogenerator (SH-TENG) to convert mechanical movements into electrical energy that can be applied to next-generation wearable devices.Their measured open circuit voltage, short circuit current, short-circuit charge quantity were 240 V, 2.20 μA, 20 nC, respectively. In addition, the PU-BPAF based SH-TENG exhibited better self-cleaning ability (83%) than that of PU-BPA elastomer, which was attributed to the introduction of trifluoromethyl reducing the surface energy of the material. Consequently, PU-BPAF showed great potentials as a self-healable and stretchable conductor to be applied to flexible electronic devices.

Supramolecular polyurea hydrogels with anti-swelling capacity, reversible thermochromic properties, and tunable water content and mechanical performance

Supramolecular polyurea (PU) hydrogels with combined anti-swelling capacity, thermochromic properties, and tunable water content and mechanical performance were obtained by immersing phase separated PU films with hydrophilic soft segments in water till swelling equilibrium. The multiple H-bonds within hard-segment domains are critical to the swelling and mechanical properties, which were rationally designed by using simultaneously two aliphatic diisocyanates with different symmetry and varying molar ratio. Consequently, the hydrogels exhibit a wide range of equilibrium water content (57–80%), elastic modulus (22–476 kPa), breaking strength (33–1720 kPa), and elongation at break (160–1460%). The hydrogels also exhibit fast recovery during cyclic loading-unloading. The incorporation of strong quadruple H-bonds into hard-segment domains endowed the hydrogels with stable anti-swelling capacity. Additionally, the hydrogels changed from transparent to opaque reversibly upon heating and cooling, originating from the phase transition of soft segments. The developed supramolecular PU hydrogels show promising potentials in many fields like smart windows.

A Robust Self-healing Polyurethane Elastomer Enabled by Tuning the Molecular Mobility and Phase Morphology through Disulfide Bonds

Elastomer with outstanding strength, toughness and healing efficiency is highly promising for many emerging fields. However, it is still a challenge to integrate all these beneficial features in one elastomer. Herein, an asymmetric alicyclic structure adjacent to aromatic disulfide was tactfully introduced into polyurethane (PU) elastomer. Specifically, such elastomer (PU-HPS) was fabricated by polycondensing polytetramethylene ether glycol (PTMEG), isophorone diisocyanate (IPDI) and p-hydroxydiphenyl disulfide (HPS) via one-pot method. The molecular mobility and phase morphology of PU-HPS can be tuned by adjusting the HPS content. Consequently, the dynamic exchange of hydrogen and disulfide bonds in the hard segment domains can also be tailored. The optimized sample manifests outstanding tensile strength (46.4 MPa), high toughness (109.1 MJ m-3), high self-healing efficiency of fractured samples (90.3 %), complete scratch recovery (100 %) and good puncture resistance. Therefore, this work provides a facile strategy for developing robust self-healing polymers.

Microstructural evolution of polyurea under hydrostatic pressure

Polyurea (PU) is a versatile high strain rate elastomeric polymer that has attracted significant interest due to its utility as a blast and ballistic resistant coating. Predictive design of PU materials, particularly with a focus on structure, is complicated by the occurrence of both high pressure and high strain rate effects in response to blast and ballistic impact. To help elucidate the behavior of PU under such conditions, we sought to characterize the microstructural evolution of PU under hydrostatic compression. To this end, we utilized a diamond anvil cell with in-situ X-ray scattering to monitor the compression-induced microstructural changes of two PU materials differing in their soft segment length. We found that regardless of soft segment length, the initially phase separated structure becomes increasingly mixed during hydrostatic compression up to ~1 GPa. Despite this increase in phase mixing, the interchain network between urea linkages formed through hydrogen bonds remains apparent at pressures well above 1 GPa. The mean spacing associated with the interchain hydrogen-bonded network within the hard segment domains contracts under hydrostatic compression and in some cases recovers upon load removal. Furthermore, the extent of both deformation and recovery depends upon the degree of microphase separation as dictated by the length of the soft segment, wherein PU with a longer soft segment deforms less and recovers more.

New Stratagem for Designing High‐Performance Thermoplastic Polyurethane by Using a New Chain Extender

AbstractThe high content and regular distribution of hard segment (HS) are necessary to achieve high‐performance thermoplastic polyurethane (TPU), and the HS unit of TPU is generated from the reaction of diisocyanate and chain extender. However, the traditional chain extenders are mainly aliphatic diol that cannot provide rigid groups to improve polyurethane performances. Herein, a novel chain extender bis(hydroxyethyloxycarbonylamino)hexane (BHH) that contains two urethane groups is designed and used to construct high‐performance TPU by increasing content and regular distribution of HS. BHH is synthesized using ethylene carbonate (EC) and hexamethylenediamine (HDA) via a ring‐opening reaction. Subsequently, the effect of BHH on the polyurethane performances is studied with respect to a typical TPU by using polytetramethylene ether glycol (PTMG) and hexamethylene diisocyanate (HDI) as the starting materials. The amount of HDI considerably differs for each polyurethane, aiming to ensure the same total content of urethane groups. When compared with the traditional ethylene glycol‐extended polyurethane, the size and distribution of the HS domains of the BHH‐extended polyurethane are obviously more homogeneous, which proves BHH‐extended polyurethane has better microphase separation. Furthermore, ordered hydrogen bonding, the mechanical properties, and heat‐resistance performance are significantly improved, suggesting a potential method to design TPU delivering outstanding performance.

Fluorescence visualization directly monitors microphase separation behavior of shape memory polyurethanes

Shape memory polyurethanes (SMPUs) with excellent shape memory effects (SMEs) can be served as a kind of smart materials capable of responding to external stimuli. Microphase separation behavior between soft and hard segments of SMPUs is recognized as structural basis and an intrinsic factor for SMEs of SMPUs. Therefore, effective detection of microphase separation behavior is highly desired in order to clarify the mechanism of SMEs and further regulate the SMEs of SMPUs. Although great progresses have been made in detection of microphase separation behavior of SMPUs, non-destruction and real-time visualization for tracking the microphase separation behavior during the shape memory process of SMPUs remains a great challenge. Herein, a facile fluorescence visualization method is presented to directly, fast and nondestructively monitor the microphase separation behavior of SMPUs. Specifically, a series of novel inherent fluorescent SMPUs (IFPUs) with different hard segment contents (10%, 15% and 20%) were first prepared by using a fluorescent small molecule as part of their hard segments. It was found that this fluorescent molecule could visualize the aggregation of hard segments and the corresponding microphase separation behavior in a real-time manner. Moreover, by conducting a semi-quantitative calculation of the collected fluorescent images, the size, aspect ratio and orientation of the hard segment domains could be obtained. The results indicated that increasing the contents of hard segments could enhance the microphase separation and both stretching (50%, 100% and 200%) and subsequent recovering processes could promote the formation of larger and longer hard segment domains tending to take a perpendicular orientation to stretching.