Multiblock Poly Research Articles

Partially Fluorinated Multiblock Poly(arylene ether sulfone) Membranes for Fuel Cell Applications

AbstractSulfonated poly(arylene ether sulfone) (SPAES‐F series) membranes, which are partially fluorinated multiblock polymers containing Bisphenol 6F (6F‐BPA), are synthesized. The membranes exhibit less water uptake and higher ion conductivity at similar ion exchange capacity (IEC) values compared to previous SPAES membranes containing identical hydrophilic blocks. This is attributed to the presence of 6F‐BPA in the hydrophobic block, which enhances hydrophobicity and promotes phase separation, as observed through transmission electron microscopy analysis. F4 (IEC = 2.4 meq g−1) shows superior ion conductivity than Nafion NRE212 membrane irrespective of the humidity level. Furthermore, the SPAES electrolyte membrane of 1.5 meq g−1 produces better performance than NRE212, yielding a current density of 488 mA cm−2 at 80 °C, 80% RH, and 0.6 V. In 50% RH at 80 °C, SPAES with 1.5 meq g−1 exhibits a cell resistance and fuel cell performance comparable to those of NRE212; clearly, regulating hydrophobicity and hydrophilicity is crucial for enhanced performance.

Tuning quaternary ammonium ionomer composition and processing to produce tough films

Multi-block and random quaternary ammonium poly (arylene ether sulfone) copolymer ionomers were synthesized using sequential reactions. Ionomer film processing involved two separate methods: heterogeneous-conversion and solution-casting a pseudo-solution. Film hydroxyl conductivity, water swelling, and tensile strength were dependent upon the hydrophilic and hydrophobic block-length. 1H nuclear magnetic resonance was used to evaluate brominated multi-block poly (arylene ether sulfone) composition, degree of functionalization (DF), and ion-exchange capacity (IEC). In general, multi-block ionomer hydroxyl conductivity was greater than its randomly functionalized counterpart at a similar IEC. Multi-block ionomer films with largest hydrophilic block length exhibited a hydroxide conductivity of 49.8 mS/cm. However, the equivalent random copolymer's conductivity was 1.02 times lower with a water uptake of 223 wt%, which were 190% higher than its multi-block counterpart. This was attributed to ion-clustering improvements, which is not present in a random ionomer. Equivalent copolymer ionomers had a percolation threshold associated with excessive swelling when its IEC exceeded 2.02 meq/g. In contrast to the random ionomer, the maximum swelling observed for the multi-block copolymers was 33.6% at an IEC of 2.86 meq/g. This swelling suppression at high IEC was attributed to the sequential hydrophilic-hydrophobic block architecture. Moreover, the solution-cast multi-block ionomer was found to possess the highest toughness of 1185 × 104 J/m3, which was 237% greater than its heterogeneous counterpart. These results suggest that block length and ionomer processing play a critical role in controlling swelling, improving mechanical strength, and enhancing ion transport.

One-Pot Versatile Synthesis of Branched-Multiblock Copolymers Based on Polylactide and Poly(ε-caprolactone)

To generate a scalable and economical approach for preparing tough poly(l-lactide) (PLLA) materials, a series of branched multiblock poly(e-caprolactone)/poly(l-lactide) (BLCL) was synthesized using 3-isocyanatopropyltriethoxysilane (IPTS) as a coupling agent. Triblock poly(l-lactide)-b-poly(e-caprolactone)-b-poly(l-lactide)s (HO-LCL-OH) were synthesized by ring-opening polymerization of l-lactide using polycaprolactone diol as macroinitiator. The branched copolymers, BLCL, were then synthesized with IPTS as a chain extender. The effects of IPTS/HO-LCL-OH ratio on the thermoplasticity and tensile properties were investigated. The copolymers obtained were fabricated into films by hot press molding. The branched multiblock copolymers exhibited good thermoplasticity and remarkable toughness. Using this facile synthetic technique, various diol soft segments might be introduced into PLLA chain to prepare ductile PLLA material.

Highly Proton Conducting Polyelectrolyte Membranes with Unusual Water Swelling Behavior Based on Triptycene-containing Poly(arylene ether sulfone) Multiblock Copolymers.

Multiblock poly(arylene ether sulfone) copolymers are attractive for polyelectrolyte membrane fuel cell applications due to their reportedly improved proton conductivity under partially hydrated conditions and better mechanical/thermal stability compared to Nafion. However, the long hydrophilic sequences required to achieve high conductivity usually lead to excessive water uptake and swelling, which degrade membrane dimensional stability. Herein, we report a fundamentally new approach to address this grand challenge by introducing shape-persistent triptycene units into the hydrophobic sequences of multiblock copolymers, which induce strong supramolecular chain-threading and interlocking interactions that effectively suppress water swelling. Consequently, unlike previously reported multiblock copolymer systems, the water swelling of the triptycene-containing multiblock copolymers did not increase proportionally with water uptake. This combination of high water uptake and low swelling behavior of these copolymers resulted in excellent proton conductivity and membrane dimensional stability under fully hydrated conditions. In particular, the triptycene-containing multiblock copolymer film with the longest hydrophilic block length (i.e., BPSH100-TRP0-15k-15k) had a water uptake of 105%, an excellent proton conductivity of 0.150 S/cm, and a volume swelling ratio of just 29% (more than 42% reduction compared to Nafion 212).

Highly selective multi-block poly(ether-urea-imide)s for CO2/N2 separation: Structure-morphology-properties relationships

Polyethylene oxide (PEO)-containing multi-block copolymers are good candidates for CO2 membrane separations because of their strong affinity for CO2 but PEO crystallization and weak mechanical properties are two limitations to be overcome at high PEO content. In this work, PEO block incorporation within new linear multi-block copolymers avoided PEO crystallization. The copolymers consisted in Jeffamine soft blocks (SB) and particularly stiff urea-imide hard blocks for improved physical cross-linking and excellent film-forming ability. Varying the SB content from 41 to 70 wt% led to different copolymer physical properties, morphology and CO2 permeation properties. The copolymer with the lowest SB content was a rigid glassy material with very weak phase separation. Its soft and hard blocks formed large interpenetrated domains, resulting in low CO2 permeability (2 Barrer) but extreme selectivity (αCO2/N2 = 207) for CO2/N2 separation at 2 bar and 35 °C. CO2 permeability greatly improved with the SB content due to strong phase separation. The copolymer with the highest SB content was a thermoplastic elastomer with soft blocks forming well-separated highly permeable percolating nano-domains. Its CO2 permeability (57 Barrer) and high selectivity (αCO2/N2 = 50) are among the best properties reported for PEO-containing multi-block copolymers for CO2 capture.

Synthesis and Characterization of Multiblock Poly(Ester-Amide-Urethane)s

ABSTRACTIn this study, a multiblock copolymer containing oligo(3-methyl-morpholine-2,5-dione) (oMMD) and oligo(3-sec-butyl-morpholine-2,5-dione) (oBMD) building blocks obtained by ring-opening polymerization (ROP) of the corresponding monomers, was synthesized in a polyaddition reaction using an aliphatic diisocyanate. The multiblock copolymer (pBMD-MMD) provided a molecular weight of 40,000 g·mol−1, determined by gel permeation chromatography (GPC). Incorporation of both oligodepsipeptide segments in multiblock copolymers was confirmed by 1H NMR and Matrix Assisted Laser Desorption/Ionization Time Of Flight Mass Spectroscopy (MALDI-TOF MS) analysis. pBMD-MMD showed two separated glass transition temperatures (61 °C and 74 °C) indicating a microphase separation. Furthermore, a broad glass transition was observed by DMTA, which can be attributed to strong physical interaction i.e. by H-bonds formed between amide, ester, and urethane groups of the investigated copolymers. The obtained multiblock copolymer is supposed to own the capability to exhibit strong physical interactions.

Improvement of thermal stability, crystallinity and degradation of poly(butylene carbonate) by incorporation of bio‐based poly(ethylene sebacate) segment

Multiblock poly(carbonate‐co‐esters) (PBC‐PESe) containing poly(butylene carbonates) (PBC) and bio‐based poly(ethylene sebacate) (PESe) had been synthesized successfully by chain‐extension of dihydroxyl terminated PBC (PBC‐OH) and PESe (PESe‐OH) using 1,6‐hexmethylene diisocyanate as chain extender. The chemical structures, molecular weights, crystallization behaviors, and thermal and degradation properties of the copolymers were all characterized by proton nuclear magnetic resonance spectroscopy, Fourier transform infrared spectroscopy, gel permeation chromatography, differential scanning calorimetry, polarized optical microscope, thermogravimetry analysis, water contact angle, and hydrolytic degradation. The resulting copolymers PBC‐PESe all had a sole glass transition temperature (Tg), indicating the two segments, PBC and PESe, were well compatible in the amorphous phase. PESe segment acted a significant role on enhancing the thermal degradation temperature and hydrolytic degradation rate of multiblock copolymers. And the crystallization rate of PBC got dramatically accelerated after PESe segment was incorporated. However, the crystallization mechanism did not change. Furthermore, the mechanical properties of multiblock copolymers could be adjusted by changing the feed composition. Copyright © 2017 John Wiley & Sons, Ltd.

Influence of hydrophobic block length and ionic liquid on the performance of multiblock poly (arylene ether) proton exchange membrane

The present article includes the synthesis of nanophase-separated poly (arylene ether) multiblock copolymers. A series of poly (arylene ether sulfone) hydrophobic oligomers consisting of bisphenol-A groups were reacted with a disulfonated poly (arylene ether ketone) hydrophilic oligomer containing 4, 4′- bis (4-hydroxyphenyl) valeric acid moieties to prepare multiblock copolymers. The synthesized oligomers and block copolymers were characterized by using FT-IR, 1H NMR spectra and Gel Permeation Chromatography. The membranes obtained by solution casting method exhibited good dimensional and thermal stability. The increase in hydrophobic block length reduced the water uptake and methanol permeability of the membranes. The complexation of multiblock copolymer with ionic liquid (1-butyl-3-methyl-imidazolium tetrafluoroborate) resulted into novel hybrid membranes. These showed enhanced proton conductivity without affecting the mechanical stability. The Fenton's test revealed that the hybrid multiblock membranes were stable towards radical oxidation. The hydrophobic-hydrophilic phase separation was characterized by using tapping mode Atomic Force Microscopy (AFM). The hybrid membranes showed better fuel cell performance than that of pristine membrane.

Multiblock poly(Phenylene ether nitrile)s with pendant sulfoalkoxyl side chain for H2/air fuel cells at low humidity condition

ABSTRACTA series of multiblock poly(phenylene ether nitrile)s with pendant sulfoalkoxyl side chains have been developed as proton exchange membranes for fuel cells. The membranes were obtained by a solution casting method and exhibited good thermal stability, flexibility, and mechanical strength. The membranes displayed well‐developed microphase separation, which largely contributed to their excellent ion conduction ability. One of the new membranes with a low ion exchange capacity of 1.57 mequiv g−1 showed higher proton conductivity than Nafion 212 over the entire RH range (30–95%). The maximum power output generated in a single cell test reached up to 0.754, 0.640, and 0.414 W cm−2 at 70 °C under 80%, 50%, and 30% RH conditions, respectively. The current density of the membrane obtained at 0.6 V (I0.6) was as high as 640 mA cm−2, which was much higher than that of Nafion 212 (375 mA cm−2 at 30% RH), suggesting its superiority for a more rapid system start‐up. Furthermore, the in situ durability test at 50% RH was performed at a constant current loading, and the membrane did not show any significant voltage reduction over the 400 h testing period. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017, 55, 1940–1948

PCL-based thermo-gelling polymers for in vivo delivery of chemotherapeutics to tumors

The synthesis of a multiblock poly(ether ester urethane)s comprising poly(ε-caprolactone), poly(ethylene glycol), and poly(propylene glycol) segments is described. We found that this polymer possessed a critical thermo-gelation concentration of 4wt%. Molecular characterization of the polymer was performed in terms of molecular weight determination, chemical composition elucidation and functional group determination using GPC, NMR, and FTIR. We carried out in vitro paclitaxel and doxorubicin release studies and demonstrated that sustained therapeutic release of about 2weeks can be obtained with this system. A nude mice model of tumor was developed and intratumoral injection of therapeutic-loaded thermo-gel demonstrated that PTX-loaded thermo-gel effectively inhibited the growth of tumors.

Well-defined multiblock poly(vinylidene fluoride) and block copolymers thereof: a missing piece of the architecture puzzle.

Unprecedented synthesis of multiblock poly(vinylidene fluoride) (PVDF, up to 16 300 g mol-1) with narrow-dispersity blocks (Đ = 1.26) mediated by a fluorinated cyclic xanthate via reversible addition-fragmentation chain transfer (RAFT) polymerization is reported. The as-synthesized multiblock PVDF was employed as a macroRAFT agent to prepare valuable multiblock copolymers with potential applications in emerging areas.

Synthesis and characterization of biodegradable multiblock poly(carbonate-co-esters) containing biobased monomer

Multiblock poly(carbonate-co-esters) (PBC-PBSe) containing poly(butylene carbonates) (PBC) and poly(butylene sebacate) (PBSe) were synthesized successfully via chain-extension of dihydroxyl terminated PBC (PBC-OH) and PBSe (PBSe-OH) using 1,6-hexmethylene diisocyanate (HDI) as chain extender. The chemical structures, molecular weights, crystallization behaviors, thermal, degradation as well as mechanical properties of the copolyesters were characterized by Proton nuclear magnetic resonance spectroscopy (1H NMR), Fourier transform infrared spectroscopy (FT-IR), Gel permeation chromatography (GPC), Differential scanning calorimetry (DSC), Thermogravimetry analysis (TGA), hydrolytic degradation and mechanical testing, respectively. The results indicated that the introduction of PBSe segment not only significantly enhanced the crystallization rate of PBC, but also displayed the same crystallization mechanism within the investigated crystallization temperature range despite of the variation of the PBSe segment content. Furthermore, the thermal stability and hydrolytic degradation rate of PBC-PBSe multiblock copolymers increases with increasing PBSe content. The mechanical properties of copolymers can be adjusted by changing the feed composition.

Synthesis and characterization of multi-block poly(arylene ether sulfone) membranes with highly sulfonated blocks for use in polymer electrolyte membrane fuel cells

We synthesized novel sulfonated poly(arylene ether sulfone)s (SPAESs) multi-block copolymer membranes containing highly sulfonated hydrophilic blocks. Two different kinds of multi-block SPAESs sharing the same structure of hydrophobic blocks were proposed to investigate the membrane properties based on the effects of the hydrophilic blocks bearing sulfonic acids. The higher local concentration and acidity of the sulfonic acid groups in the hydrophilic block induced higher proton conductivity. The block SPAESs showed comparable proton conductivities to those of the state-of-the-art perfluorinated sulfonic acid (PFSA) membranes, and their transmission electron microscopy (TEM) images revealed a well-developed phase separation. In particular, the SPAES 4 X10Y10 membrane showed excellent proton conductivity, which was higher than that of the PFSA over the entire relative humidity (RH) range at 80°C. Moreover, the multi-block SPAES membranes showed a comparable fuel cell performance to the Nafion membranes, even at 50% and 30% RH.

Recent Advances of Poly(ether-ether) and Poly(ether-ester) Block Copolymers in Biomedical Applications.

Poly(ether-ether) and poly(ether-ester) block copolymers have been widely applied in biomedical fields over two decades due to their good safety and biocompatibility. Poly(ethylene glycol), poly(ethylene glycol)-poly(propylene glycol) and poly(lactic-co-glycolic acid) have been approved as excipients by Food and Drug Administration. Because of the broad perspective in biomedical fields, many novel poly(etherether) and poly(ether-ester) block copolymers have been developed for drug delivery, gene therapy and tissue engineering in recent years. This review focuses on active targeting theranostic systems, gene delivery systems and tissue engineering based on poly(ether-ether) and poly(ether-ester) block copolymers. We perform a structured search of bibliographic databases for peer-reviewed scientific reports using a focused review question and inclusion/exclusion criteria. The literatures related to the topics of this review are cataloged according to the developed copolymers or their applications such as active targeting theranostic systems, gene delivery systems and tissue engineering. Some important advances and new trends are summarized in this review. Some commercial poly(ether-ether) copolymers have been used as excipients for drug research and development. Amphiphilic and biodegradable poly(ether-ester) diblock copolymers are capable of formulating biomedical nanoparticulate theranostic systems, and targeting moiety-functionalized poly(ether-ester) diblock copolymers will be further developed and applied in biomedical nanotechnology fields in the near future. Meanwhile, triblock or multiblock poly(ether-ether) and poly(ether-ester) copolymers with environmentsensitive properties are suitable for gene delivery and tissue engineering. Poly(ether-ether) and poly(ether-ester) copolymers are being extensively applied in active targeting theranostic systems, gene delivery systems and tissue engineering. Biodegradable, environment-sensitive and targeting moiety-functionalized block copolymers, which are being applied in active targeting theranostic systems, gene delivery systems and tissue engineering, are promising candidates for treatment of various diseases.

Gas permeability, mechanical behaviour and compostability of fully-aliphatic bio-based multiblock poly(ester urethane)s

Bio-based and compostable poly(ester urethane)s with tailorable mechanical and gas barrier properties designed for packaging purposes.

Design of fully aliphatic multiblock poly(ester urethane)s displaying thermoplastic elastomeric properties

By the combination of prepolymers with very different physical/chemical properties, better performance materials can be obtained. In the present study, three hydroxyl-terminated fully aliphatic polyesters have been chain extended to prepare new multiblock poly(ester urethane)s (PEU) displaying thermoplastic elastomeric characteristics. Poly(butylene succinate), poly(1,4-cyclohexylenedimethylene-1,4-cyclohexanedicarboxylate), and poly(neopentyl glycol adipate) have been respectively used as soft-hard, hard and soft segment. The evaluation of molecular, thermal, and mechanical properties and hydrolytic degradation profile permitted to correlate the behavior of the so-obtained materials with their molecular structure, and highlighted that it is possible to nicely tune the final characteristics of this class of PEUs by just varying the mutual amount of the three segments.

Telechelic Poly(methyl acrylate)s as Constituents for Multiblock Poly(urethane urea)s

New poly(urethane urea)s based on telechelic poly(methyl acrylate)s (PMAs) and different diisocyanates and diamines are prepared by a two‐step polyaddition process—formation of an isocyanate telechelic prepolymer followed by chain extension with a diamine to form the final poly(urethane urea)s. Hydroxyl‐telechelic or mixed amino‐hydroxyl‐telechelic PMAs are obtained by two different concepts: (i) according to the first concept methyl acrylate (MA) was polymerized by single electron transfer‐living radical polymerization (SET‐LRP) using 2‐hydroxyethyl 2‐bromoisobutyrate as initiator followed by nucleophilic substitution of the halogen end group with n‐butylamine, 2‐methylamino ethanol, or 3‐amino‐1‐propanol and (ii) according to the second concept after SET‐LRP under the same conditions the halogen end group is converted to an azide followed by a click reaction using sodium azide and propargyl alcohol in a one‐pot reaction. Applying the second concept, a hydroxyl‐functional PMA with a share of 83 mol% bifunctionality is obtained. This PMA‐diol is used in polyaddition reaction with different diisocyanates (isophorone diisocyanate (IPDI), 4,4′‐methylenebis(cyclohexyl isocyanate) (HMDI), and 4,4′‐methylenediphenyl diisocyanate (MDI)) resulting in an isocyanate‐telechelic prepolymer followed by chain extension with the corresponding diamines (isophorone diamine (IPDA), 4,4′‐methylenebis(cyclohexyl amine) (HMDA), and 4,4′‐methylenediphenyl diamine (MDA)). The polyurethane based on hydroxyl‐telechelic PMAs and IPDI/IPDA has a molecular weight of Mn = 44 500 g mol−1 and a dispersity Đ = 3.5, respectively; those based on HMDI/HMDA and MDI/MDA have Mn = 24 600 g mol−1 and Đ = 2.2 and Mn = 16 100 g mol−1 and Đ = 2.0, respectively. image

Investigation of the synthesis of poly-D,L-lactide-co-poly(ethylene glycol) flexible thermoplastic

ABSTRACTA series of biodegradable poly(D,L-lactide)-poly(ethylene glycol) multiblock poly(ether-ester-urethane)s with various lactide-to-poly(ethylene glycol) (LA/PEG) mole ratios has been successfully synthesized by ring-opening polymerization (ROP) followed by chain extension reaction through formation of urethane linkage. Resulting FT-IR spectra indicate complete polymerization of lactide monomers, while NMR analysis quantitatively marks the chain length of polymer blocks. The molecular weight and dispersion index of copolymers were investigated by GPC analysis. DSC thermogram and XRD diffractogram of the prepared copolymers were studied as well for revealing the thermal and crystallinity behavior of the copolymer as LA/PEG mole ratios varied.

Polymer Electrolyte Membranes Based on Multiblock Poly(phenylene ether ketone)s with Pendant Alkylsulfonic Acids: Effects on the Isomeric Configuration and Ion Transport Mechanism

Two structural variations of multiblock poly(phenylene ether ketone)s (bSPPEKs) with pendant alkylsulfonic acids were prepared by a polycondensation reaction between oligomeric difluoro and diphenoxide precursors, followed by successive demethylation and sulfonation processes. Two isomers, bis[4-fluoro-3-(4′-methoxylbenzoyl)]biphenyl (p-BFMBP) and bis[5-fluoro-2-(4′-methoxylbenzoyl)]biphenyl (m-BFMBP), were prepared as the difluoro starting monomers. The corresponding polymer membranes were obtained with good mechanical stability to facilitate the further characterizations. The morphology of bSPPEKs was confirmed by atomic force microscopy, from which the distinct phase separation could be identified with the average hydrophilic domain size of ca. 15–20 nm for the m-bSPPEKs. It is worth noting that both m- and p-bSPPEKs show quite comparable, or even better, ion conduction capacities than commercially available Nafion membrane, especially under low relative humidity conditions (30–50%), suggesting their p...

Synthesis and characterization of crosslink-free highly sulfonated multi-block poly(arylene ether sulfone) multi-block membranes for fuel cells

Highly sulfonated hydrophilic block polymers were designed and the resultant block membrane showed very high proton conductivity even under low RH.