PCL Segments Research Articles

Electrospun Polylactide-Poly(ε-Caprolactone) Fibers: Structure Characterization and Segmental Dynamic Response.

Electrospun ultrathin fibers based on binary compositions of polylactide (PLA) and poly(ε-caprolactone) (PCL) with the various content from the polymer ratio from 0/100 to 100/0 have been explored. Combining thermal (DSC) and spectropy (ESR) techniques, the effect of biopolymer content on the characteristics of the crystal structure of PLA and PCL and the rotative diffusion of the stable TEMPO radical in the intercrystallite areas of PLA/PCL compositions was shown. It was revealed that after PLA and PCL blending, significant changes in the degree of crystallinity of PLA, PCL segment mobility, sorption of the Tempo probe, as well as its activation energy of rotation in the intercrystalline areas of PLA/PCL fibers, were evaluated. The characteristic region of biopolymers' composition from 50/50 to 30/70% PLA/PCL blend ratio was found, where the inversion transition of PLA from dispersive medium to dispersive phase where an inversion transition is assumed when the continuous medium of the PLA transforms into a discrete phase. The performed studies made it possible, firstly, to carry out a detailed study of the effect of the system component ratio on the structural and dynamic characteristics of the PLA/PCL film material at the molecular level.

Polyester networks based on Tulipalin A and ε‐caprolactone and activation of the Thioether groups by incorporation of trialkylsulfonium salts

AbstractLinear and star‐shaped poly(ε‐caprolactone‐co‐α‐methylene‐γ‐butyrolactone) P(CL‐co‐MBL) copolyesters with a pendant functional double bond of α‐methylene‐γ‐butyrolactone (MBL) comonomer were used as polymeric precursor for organo‐gels formation. Crosslinking was carried out by light‐initiated thia‐Michael reaction using 1,5‐pentanedithiol (PDT) and pentaerythritol tetrakis(3‐mercaptopropionate) (PETK). Double bond conversion and the content of free thiol groups in the obtained networks was followed and rationally estimated using confocal Raman spectroscopy. The gel content and the crosslinking density varied based on MBL comonomer and crosslinker content and were highest for slight thiol to double bond excess (SH/vinyl; 2/1 molar ratio) while decreasing with further thiol excess. These parameters were more pronounced by the replacement of linear PDT with the star‐shaped PETK crosslinker. The thermal and rheological properties investigation of the obtained materials was performed employing DSC, TGA and using frequency and temperature sweeps rheological measurements. Shear moduli in the range 0.14 up to 0.93 MPa were obtained due to different content of MBL in pre‐polymer and crosslinker in network formation. The strength was caused by the crystalline phase of the PCL segments up to a temperature of 50°C. Formed thioether bond within the network were not reversible up to 150°C as it was found based on temperature sweep rheology. Following, the activation and conversion of thioether bonds within the obtained materials into trialkylsulfonium salts was attained through the alkylation using butyl brosylate. The dynamic nature of the transalkylation at elevated temperature 150°C allowed network rearrangement, which was proved by stress relaxation experiment and investigation of the self‐healing capabilities.

Synthesis and Self-assembly of a Novel Amphiphilic Tri-arm Star-shaped Copolymer Poly(ethylene oxide)-b-Poly(ε-caprolactone)

Abstract:Amphiphilic tri-arm star-shaped copolymers, poly(ethylene oxide)-b-poly(ε-caprolactone) PEO3-b-PCL3, with different poly (ε-caprolactone) (PCL) molecular weights were successfully synthesized by ring-opening polymerization (ROP). Firstly, the tri-arm star-shaped PEO3 was prepared by ROP of trimethylolpropane and ethylene oxide (EO). The ring-opening polymerization (ROP) of ε- caprolactone (CL) was initiated using the tri-arm star-shaped PEO3 with the hydroxyl group as macroinitiator and Sn(Oct)2 as a catalyst. Amphiphilic tri-arm star-shaped copolymers PEO3-b-PCL3 were obtained. By changing the ratio of monomer and macroinitiator, a series of PEO3-b-PCL3 were prepared with a well-defined structure, molecular weight control, and narrow molecular weight distribution. The expected intermediates and final products were confirmed by 1H NMR and Gel Permeation Chromatography (GPC) analyses. In addition, the sizes and morphologies of the obtained micelles with different PCL segment lengths were investigated with dynamic light scattering (DLS) and transmission electron microscopy (TEM), respectively. It was found that the self-assembly morphologies were spherical micelle in aqueous solution.

Poly(L‐lactide)‐b‐poly(ε‐caprolactone)‐b‐poly(D,L‐lactide) copolymers with enhanced toughness and strength by regulating crystallization and phase separation

AbstractCopolymerizing poly(lactide) with other materials to obtain better comprehensive performance is a effective way to expand its application range. In this work, the precursors of hydroxyl terminated (poly(L‐lactide) [PLLA], poly(ε‐caprolactone) [PCL], poly(D,L‐lactide) [PDLLA]) were prepared, and PLLA‐PCL‐PDLLA copolymer were synthesized by chain extension. The effects of the proportion and molecular weight of each component and the amount of chain extender on crystallization, phase structures, mechanical properties and thermal stabilities of PLLA‐PCL‐PDLLA copolymer were studied in detail. Based on small‐angle X‐ray scattering results, the competition between crystallization and microphase separation was regulated by the composition and chain length of prepolymers. As the ratio of PLLA/PDLLA was 1:1, crystallization was prevailing and no obvious peak was observed in SAXS pattern. The tensile test results showed that as the ratio of PLLA/PDLLA increased from 1:1 to 1:5, the elongation at break of the copolymer changed from 1.8% to 343%. By using shorter length of PCL and PLLA segments in chain extension, improvement in strength and flexibility were obtained due to moderate degree of crystallization and microphase separation. This work used biodegradable materials to prepare extraordinary toughness copolymers without losing the biocompatibility, which may provide a feasible method for obtaining high toughness and biodegradable PLA‐based materials.

Facile synthesis of calabash-shaped and twin-tail tadpole-shaped copolymers via photothermal-induced topological transformation

Rational design of architecture-transformable polymers with dynamic covalent bonds allows to form multiple ring-bearing analogues and gain insight into topology-tunable physicochemical properties. To reveal unique properties originating from size-asymmetric twincycles and ring-linear conjugates, twin-tail tadpole-shaped (TTP) and calabash-shaped bicyclic (CLB) copolymers comprising poly(ε-caprolactone) (PCL, A) and polystyrene (PSt, B) segments are synthesized. Controlled polymerization and radical trap-assisted atom transfer radical coupling are combined to synthesize a multisite telechelic ABA. By virtue of UV-induced intramolecular anthracene dimerization and selective thermolysis of in-chain alkoxyamine and anthracene dimer linkers of the macrocycle, versatile topological transformations from linear copolymer to TTP, CLB and ring/tail-reversal TTP are achieved. Owing to distinct chain architectures, three types of analogues can exhibit some differences in hydrodynamic volume, crystallization, diffusion coefficient and aggregation behavior, revealing pronounced topology effect. This study affords a promising method to construct stimuli-labile ring-bearing architectures to reveal topology-dependent properties.

Toward regulating biodegradation in stages of polyurethane copolymers with bicontinuous microphase separation.

For typical biodegradable polymers, their overall performance almost declines exponentially to the degradation degree, which inevitably leads to a dilemma between the requirements of service life and retention time in the environment (both in vitro and in vivo). It is a great challenge to develop a biodegradable polymeric device with relatively stable performance in service while rapidly degrading out of service. Herein, we demonstrate an effective strategy to control degradation of biodegradable polymers in stages by constructing separated bicontinuous microphases with very different microphase degradation rates. First, polyurethane copolymers (PCL-b-CrP-U) containing two blocks, i.e., semicrystalline poly(ε-caprolactone) (PCL) blocks and amorphous random copolymer blocks (CrP) based on ε-CL and p-dioxanone (PDO), were synthesized. The microscopic morphology of PCL-b-CrP-U is investigated by an alkali-accelerated degradation experiment, which also demonstrates that the chain cleavage-induced crystallization during degradation resulted in a self-reinforcement by forming degradation residues with a scaffold-like morphology. The tensile test shows that PCL-b-CrP-U has excellent mechanical properties (1500% of elongation at break, a tensile strength of about 7.5 MPa, and an elastic modulus of 40.0 MPa). The degradation experiments with artificial pancreatic juice as a working medium reveal that PCL-b-CrP-U samples containing relatively high PDO units exhibit a three-stage degradation, i.e. an induction stage, a steady degradation stage and an accelerated degradation stage. The CrP phase preferentially hydrolyzes to form some microchannels due to its amorphous nature and relatively high hydrophilicity, effectively accelerating the entry of water and enzymes into the inner parts of the sample. Meanwhile, at this stage, those originally amorphous PCL segments gradually crystalize owing to their enhanced chain mobility induced by the chain cleavage, forming a "scaffold"-like structure, which effectively reinforces the sample to resist the damage from external force and therefore guarantees a relatively stable mechanical performance of PCL-b-CrP-U during service. With the further depletion of the CrP phase, the intermediate "scaffold"-like structure is also very beneficial to accelerate the degradation of residues owing to its large specific surface area, which is expected to be beneficial for preventing long-term retention of the implantation devices.

Mechanical Properties of PLA/PCL Blends Compatibilized with PEG‐b‐PCL Multiblock Copolymer

AbstractAmong the various kinds of copolymers that can be used as compatibilizers in poly (lactic acid) (PLA) and poly(ε‐caprolactone) (PCL) blends, copolymers containing segments of ε‐caprolactone and ethylene glycol (PEG) are an interesting choice because they are also biodegradable and biocompatible. A multiblock copolymer containing PEG and PCL segments, synthesized via one‐step bulk polycondensation, is added into PLA/PCL blend (80/20 wt%) at 1 and 5 wt% from the molten state, using a twin‐screw extruder. The effect of the PEG‐b‐PCL copolymer on the mechanical properties of PLA/PCL blends is investigated by tensile and Izod impact tests. The mixing of PCL with PLA does not promote adequate matrix toughness due to the incompatibility between the phases. The addition of only 1 wt% of the multiblock copolymer little changes the mechanical behavior of the blend. Only the compatibilized PLA/PCL blend with 5 wt% of the multiblock copolymer exhibits a significant increase in strain at break and notches Izod impact resistance in comparison with uncompatibilized PLA/PCL blends or neat PLA. Therefore, the addition of the PEG‐b‐PCL multiblock copolymer results in a marked change in the mechanical behavior, from brittle to ductile at room temperature, and confirms its compatibilization potential for the PLA/PCL immiscible blends.

Highly toughened poly(ʟ-lactide) by poly(ᴅ-lactide)-containing crosslinked polyurethane shows excellent malleability, flexibility and shape memory property

The brittle nature of poly(ʟ-lactide) (PLLA) limits its extensive application. In the present work, PLLA was toughened by crosslinked polyurethane (CPU), which was formed by reactive blending of poly(ε-caprolactone) (PCL), poly(d-lactide) (PDLA), hexamethylene diisocyanate (HDI) and glycerol. PCL segments in the network acted as soft segments while PDLA segments served as hard segments to form stereocomplex (SC) crystallites as physical crosslinking points. The disappearing peak at 2270 cm−1 and the emerging absorption peak appeared at 1530 cm−1 in the FTIR spectrum proved the formation of the network in the modified PLLA. The melt-quenched specimens containing the network showed significant increase in elongation at break, and the CPU80/18/2 blend showed a maximum value of 428.6%. Tensile-fractured surfaces of all the blends exhibited fibril-like morphologies because of the matrix shear yielding caused by large deformation. And the crystallization rate could be accelerated because of the PDLA chains in the sample comparing to the CPU80/20 without PDLA. Interestingly, when SC crystallites could be formed after annealing of the melt-quenched specimens at 110 °C for 1h, CPU80/18/2 still owned a maximum value of 152.8% of elongation at break. It was found that the CPU phase was presented as continuous phase in the material. Due to the compatibility, the added PDLA chains were distributed in the interface of CPU and PLLA phase, which provided additional interfacial adhesion, improved the stress transmission and endowed the material with enhanced toughness. The CPU80/18/2 sample also showed the malleability, flexibility and shape memory capacity, implying great application potential as biodegradable green composites.

Amphiphilic olefin block copolymers synthesized by successive coordinative chain transfer and ring-opening polymerizations

Introducing polarity is a necessity for widening the application scope of polyolefins specifically for developing biocompatible products. To this end, we exploit a two-step polymerization process to synthesize poly(ethylene‑b‑caprolactone) PE‑PCL block copolymers, which contain both polar and non-polar segments. First ethylene is polymerized by a generic metallocene catalyst in the presence of ZnEt2 as the chain transfer agent according to the coordinative chain transfer polymerization (CCTP) technique. Terminal zinc atoms are subsequently replaced by hydroxyl groups (PE‑OH) by exposing dormant polymer chains to oxygen. Afterward, ring-opening polymerization (ROP) of ε‑caprolactone is initiated by PE‑OH to form PE‑PCL block copolymers. Successful formation of both blocks is verified by FTIR and NMR spectroscopy. The presence of PCL blocks greatly lowers the crystallinity of ethylene sequences according to XRD and DSC results. Moreover, a second type of PE crystals with more chain folds and lower lamella thickness is found in block copolymers, which is absent in the equivalent physical blend. The diverse crystal structure of block copolymers suggest that phase separation exists between PE and PCL segments. The SEM image of the equivalent physical blend confirms the tendency of PCL and PE chains to phase separate, and infers a compatibilization in the presence of PE‑PCL block copolymers. This phase separation is detected by rheological measurements, as well, where block copolymers show deviations from Maxwell behavior in the terminal relaxation zone at low frequencies. Rheology results also show that the order-disorder transition temperature (TODT) of these block copolymers is higher than 180 °C. These results provide a clear picture from the morphology and utility of such block copolymers specifically for compatibilizing blends of polar polymers and non-polar polyolefins, which significantly broaden the utility of polyolefins.

Hydrophilic and degradable polylactones via copolymerization of ε-caprolactone and oxo-crown ether catalyzed by a bifunctional organic base

Poly(ε-caprolactone) (PCL) has been one of the most important biomaterials, but its instinct hydrophobicity and slow biodegradation limit its broad applications. Herein, copolymerization of CL and a hydrophilic macrolactone, 2-oxo-15-crown-5 ether (O15C), was achieved through ring opening polymerization catalyzed by 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) using benzyl alcohol as the initiator at room temperature. A series of poly(CL-co-O15C) copolymers with different O15C contents were prepared by simply tuning the feeding ratio of [CL]/[O15C]. They showed molecular weights ranging from 11.0 to 20.6 kg mol−1, and polydispersity index between 1.4 and 1.6, characterized by SEC (Size Exclusion Chromatography). Analysis of 1H NMR indicated that the copolymers belong to a random copolymer structure. The introduction of O15C had a significant influence on thermal stability, hydrophilicity and degradability of the copolymers. With increasing the O15C content, the crystalline ability of PCL segment among the copolymers reduced, while the hydrophilic property was improved obviously. Through hydrolysis experiment, the poly(CL-co-O15C) with O15C content of 38 mol% exhibited a much faster degradable rate than that of the copolymer with O15C content of 10 mol%. Therefore, copolymerization of CL with a crown ether monomer via organic catalyst mediated ROP will be a feasible strategy for modification of polyester materials.

Polyvinyl alcohol-waterborne blocked-based polyurethane composite surface sizing agents for enhancing mechanical performance of specialty paper

• Introduce the end-blocked structure into the water-based functional polyurethane segments applied as a “latent cross-linker” for surface sizing, • A novel compound sizing system containing water-based blocked polyurethane and polyvinyl alcohol, • Chemical bonding and hydrogen bonding between highly active isocyanate groups and paper fiber after unblocking, • Application of water-based blocked polyurethane in surface sizing of special paper. Efficient improvement of paper strength while optimized sizing technique remains challenging and fascinating since specialty paper are required to low-cost, high printing quality and environmental sustainability. Herein, a novel controlled reactivity polyester glycol-based cross-linker (TBPU) applied in paper surface sizing was exploited by simple two-steps polymerization and blending process. An end-blocked structure design strategy of containing densely distributed multiple soft segments and active hydrogen nucleophilic segments (Butanone oxime, MEKO as end closure units) in isocyanate dispersion was achieved to address the scarcity of mechanical properties and the inconvenient in surface-sizing progress. TBPU can block the NCO groups in IPDI segments at 60 °C, and NCO groups can be deblocked at the temperature higher than 110 °C, which endow TBPU with latent cross-linking property. Afterward, we took advantage of the structural feature of polyhydroxy compounds and the adhesion to cellulose via using polyvinyl alcohol (PVA) as a blending component to form TBPU/PVA emulsion. The organization of NCO groups react with hydroxyl groups, carbamate groups cross-linked with hydrogen bonds, and crystallized PCL segments generates phase-separated hierarchical domains. Serving as high-reactivity paper-sizing fillers capable of cross-linking and disintegration under an external change of temperature, the hierarchical domains can strengthen the specialty papers and enhance their water resistance and ink adhesion. The influences of TBPU content, PVA content and NCO/ OH molar ratio on the physicochemical properties of the resultant emulsions and sized paper have been investigated. As a result, the paper sized with TBPU-1.6/PVA emulsion exhibit a tensile index of ≈107.19 Nm/g, a tearing index of ≈11.79 m N • m 2 /g, a folding resistance of ≈4511 s, an optimum blending temperature of 70 °C and exceptional cooperation ratio with PVA and TBPU (4.0 wt%, 3.0 wt%), which are 1.649 times, 1.966 times, and 2.652 times than those of untreated papers (65 Nm/g, 6 m N • m 2 /g, 1701 s). Furthermore, sizing liquid can be conveniently applied and recycled due to their excellent environmental friendliness and Biodegradability, this work provides a promising solution for optimizing surface sizing technology.

Phospholipid-Conjugated PEG-b-PCL Copolymers as Precursors of Micellar Vehicles for Amphotericin B.

Amphotericin B (AmB) is a widely used antifungal that presents a broad action spectrum and few reports on the development of resistance. However, AmB is highly toxic, causing renal failure in a considerable number of treated patients. Although when AmB is transported via polymer micelles (PMs) as delivery vehicles its nephrotoxicity has been successfully attenuated, this type of nanoparticle has limitations, such as low encapsulation capacity and poor stability in aqueous media. In this research, the effect of modifying polyethyleglicol-block-poly(ε-caprolactone) (PEG-b-PCL) with 1,2-distearoyl-sn-glycero-3-phosphorylethanolamine (DSPE) on the performance of PMs as vehicles for AmB was studied. PEG-b-PCL with two different lengths of a PCL segment was prepared via ring opening polymerisation and modified with DSPE at a post-synthesis stage through amidation. Upon modification with DSPE, a copolymer was self-assembled, thereby producing particles with hydrodynamic diameters below 100 nm and a lower critical micelle concentration than that of the raw copolymers. Likewise, in the presence of DSPE, the loading capacity of AmB increased because of the formed intermolecular interactions, such as hydrogen bonds, which also caused a lower aggregation of this drug. The assessment of in vitro toxicity against red blood cells indicated that the toxicity of AmB decreased upon encapsulation; however, its antifungal action against clinical yeasts was maintained and enhanced, as indicated by a decrease in its minimum inhibitory concentration.

One-Pot Synthesis of Supertough, Sustainable Polyester Thermoplastic Elastomers Using Block-Like, Gradient Copolymer as Soft Midblock

It remains challenging to synthesize supertough thermoplastic elastomers (TPEs) since the stretchability and tensile strength are mutually exclusive. Here, we report a one-pot strategy for the prep...

Fabrication of emulsion-templated polystyrene absorbent using 4-arm star-shaped poly(ɛ-caprolactone) as property defining crosslinker

PolyHIPEs prepared by polymerizing high internal phase emulsions (HIPEs) normally have a cross-linked structure, with the cross-linking providing the mechanical stability to maintain the porous structure and prevent collapse during cure and uses. The most widely investigated polyHIPE (i.e., polystyrene (PS) polyHIPE) is cross-linked with divinylbenzene (DVB), making them rigid, brittle, and environmentally unfriendly. To address this issue, tough and recyclable PS based polyHIPEs are prepared in this work using 4-vinyl-arm star-shaped poly(ɛ-caprolactone) (4vPCL) as property defining cross-linker. Comparing poly(S-co-DVB) polyHIPE, the poly(S-co-4vPCL) polyHIPE is much less brittle and friable, with its impact strength up to 3 times higher. The viscous 4vPCL promotes the formation of small voids in polyHIPEs. Moreover, the polyHIPEs are soluble in organic solvent after the PCL segments were degraded, suggesting that the cross-linking could be “removed” and the polymers are eventually recyclable. On this basis, the porous polymers could be used to continuously separate oils from the water–oil mixture. When it is used as oil absorbent, it has full preservation of both the porous morphology and the absorption capacity in the performed ten absorption/desorption cycles.

Amphiphilic and segmented polyurethanes based on poly(ε-caprolactone)diol and poly(2-ethyl-2-oxazoline)diol: Synthesis, properties, and a preliminary performance study of the 3D printing

Polyurethanes (PU) have a wide variety of applications due to possessing tailored properties which can be imparted by composition. The combination of polyols in different ratios provide specific properties for the segmented PU, such as mechanical strength, elasticity, hydrophilicity and so on. In this work, amphiphilic and segmented polyurethanes, based on poly(ε-caprolactone)diol (PCL-diol) and poly(2-ethyl-2-oxazoline)diol (PEtOx-diol) at variable mass fractions, were synthesized by a two-step route and characterized according to composition, molar mass, thermal, dynamic mechanical, and rheological properties. Polyurethanes with molar masses ranging from 17.9 to 39.6 kDa, and a molar mass dispersity in the range of 2.0–4.0, are capable of swelling in water, with the swelling coefficient being modulated by the polyurethane composition and by the temperature because of the lower critical solubility temperature (LCST) behavior of PEtOx in an aqueous medium. PCL and PEtOx segments in the PU chains are partially miscible, therefore the polyurethanes are heterogeneous, presenting a PCL/PEtOx miscible phase dispersed in a PCL rich matrix in the solid state. PU with 50% mass fraction of PEtOx presented a gelation temperature of 69 °C, as determined by rheology, and was evaluated for Fused Deposition Modelling (FDM) 3D printing, showing promising features, although with a low resolution and fidelity to the computational project, mainly due to its high viscoelasticity which may be modulated by the molar mass of the polymer. Moreover, cell viability tests suggest that the polyurethanes are compatible with biomedical applications.

In situ preparation of hetero-polymers/clay nanocomposites by CUAAC click chemistry.

A series of polymer/clay nanocomposites containing mechanistically two different polymers, poly(ethylene glycol) (PEG) and poly(epsilon caprolactone) (PCL), were prepared by simultaneous copper(I)-catalyzed alkyne-azide cycloaddition click reactions. Both clickable polymers, PEG-Alkyne and PCL-Alkyne, were simultaneously clicked on to azide-functional montmorillonite (MMT-N3) nanoclay to get corresponding PEG-PCL/MMT nanocomposites. The chemical structures of the resulting nanocomposites were verified by following azide and silicone-oxygen bands using FT-IR and characteristic bands of PEG and PCL segments using 1H-NMR spectroscopy. The combined XRD and TEM analysis confirmed that all PEG-PCL/MMT nanocomposites had partially exfoliated/intercalated morphologies. In addition, the increase of MMT-N3 loading not only improved the onset and maximum degradation temperatures of the nanocomposites but also their char yields. Furthermore, the incorporation of MMT-N3 in the polymer matrix did not significantly influence the crystallization behavior of both PEG and PCL segments.

Inhibition effects of poly(N-vinylcaprolactam)/poly(ε-caprolactone) amphiphilic block copolymers on methane hydrate formation

Homo- and copolymers of poly(N-vinylcaprolactam) PVCap are widely used in the natural gas industry as hydrate inhibitors. However, seldom studies focus on block copolymers and the biodegradability of the polymers is not taken into account as well. In this work, amphiphilic block copolymers (PVCap-b-PCL) containing different ratio of biodegradable poly(ε-caprolactone) (PCL) and PVCap were synthesized. All the synthesized copolymers had narrow molecular distribution which ensured stable properties of the copolymers in the kinetic hydrate inhibition (KHI) performance. They also showed higher cloud point than PVCap. The effect of the PVCap-b-PCL copolymers on methane hydrate formation and hydrate micro-structure were studied. The copolymers used in the KHI experiments were in the form of micelles and they were found performed better than PVCap in the methane hydrate inhibition, providing much longer induction time and increased with higher PCL segment content. The PVCap-b-PCL copolymers have amphiphilic structure similar with surfactants making them also perform like antiagglomerants, effectively suppressing the hydrate agglomeration (less than 40μm). The possible inhibition mechanism of PVCap-b-PCL was discussed. The biodegradable PCL segment has increased the biodegradability of PVCap-b-PCL as expected, indicating that environmental friendly hydrate inhibitors can be obtained by adjusting WPCL/WPVCap ratio.

Degradable hyperbranched polymer with fouling resistance for antifouling coatings

The controlled release of antifoulant is critical in marine antifouling, which is profoundly influenced by the compatibility between polymer resin and antifoulant. Conjugation of polymers with active molecules provides a promising strategy to solve the problem. In this study, we report the synthesis of hyperbranched polymers containing antifouling main-chains and degradable branching points by using reversible addition-fragmentation chain-transfer (RAFT) polymerization. The copolymerization of butyl methacrylate, vinyl-functional Econea and divinyl-functional poly(ε-caprolactone) (PCL) yields a degradable hyperbranched antifouling polymer (DHAP). As revealed by 1H NMR, the vinyl conversion linearly increases over reaction time during RAFT polymerization with a final conversion rate above 90 % after 24 h. The branching degree of DHAP increases with the content of PCL segment. Quartz crystal microbalance with dissipation (QCM-D) measurements show the degradation of DHAP is controlled. Antibacterial assays indicate that DHAP coating has good antibacterial activity. Thus, DHAP represents a promising system for antifouling coatings.

Synthesis of Poly(ether‐ester‐urethane) with a Controlled Molar Mass Based on Poly(ε‐caprolactone) and Poly(ethylene glycol) Segments

AbstractPoly(ether‐ester‐urethanes) (PEEUs) derived from poly(ε‐caprolactone) and poly(ethylene glycol) (PCL‐b‐PEG) have a high potential for use in biomedical applications or as compatibilizers of immiscible poly(acid lactic) and poly(ε‐caprolactone) (PLA/PCL) blends. This study focused on the synthesis of PEEUs with same molar mass by one‐step bulk polycondensation of PCL and PEG macrodiols and hexamethylene diisocyanate (HDI). The copolymers, distinguished by the size of hydrophilic PEG and hydrophobic PCL segments and symmetry of the blocks, are characterized by SEC, FTIR, H1‐NMR, TGA, DSC, and water absorption testing. FTIR and H1‐NMR results demonstrated the formation of a hydroxy‐terminated multiblock copolymer with urethane bonds. Additionally, the PEG:PCL compositions measured by H1‐NMR are close to the theoretical compositions. Molar mass distribution curves revealed that copolymers with molar mass around 45 000 Da are synthesized by varying extents of ratio, given by NCO/OH molar ratio, between 0.9 and 1.0 depending on the initial macrodiols molar masses. The block size ratio of hydrophilic and hydrophobic blocks is an important parameter in water absorption behavior, which can generate a water‐uptake of 50% or even 350% depending on the symmetry of the segments.

Thermoplastic Blend Exhibiting Shape Memory-Assisted Self-Healing Functionality

Here, we report on a polymer blend consisting of a soft thermoplastic polyurethane (TPU) elastomer and a low melting temperature thermoplastic healing agent (polycaprolactone, PCL). In this study, polymer blends containing up to 60 wt % PCL were prepared and the resulting mechanical, thermal, shape memory, and self-healing properties were studied. These immiscible polymers exhibit two well-separated transitions attributable to the melting of PCL and TPU hard segments. This viscoelastic behavior engendered shape memory capability at moderate processing temperatures (∼90 °C) and melt processability at elevated temperatures (>160 °C). The reversible plasticity shape memory (RPSM) effect was also characterized: when subjected to 125% strain at room temperature and subsequently heated to 90 °C, the samples nearly fully recovered to their original length. Moreover, upon heating to above PCL's melting temperature, the flow of PCL into an undeformed crack was shown to fill the crack void, thus promoting self-repair. Through the action of mild heating (90 °C/30 min), fracture surfaces are brought into intimate contact through the action of the RPSM effect and subsequently healed through the redistribution of molten PCL. The shape memory-assisted self-healing efficiency was evaluated by comparing the tensile force restoration after healing of a highly deformed, notched sample to its behavior prior to notching. It was observed that blends containing up to 30 wt % PCL showed nearly complete restoration of properties. In contrast, pure TPU showed only about 5% healing efficiency because of the absence of the PCL healing agent. Blends containing 50 and 60 wt % PCL likewise did not exhibit appreciable restoration of properties, and this was attributed to their propensity to neck during crack opening and poor mechanical properties at elevated temperatures. Blends may serve as a self-healing replacement for pure TPU in existing applications (e.g., automotive and sporting goods) or as a self-healing shape memory polymer in advanced products in soft robotic, biomedical, and microelectronic applications.