Crystallization and Melting Behavior of Poly(3‐hydroxybutyrate)‐Based Blends

Summary: Blends of high molecular weight poly(R‐3‐hydroxybutyrate) (PHB) ( = 352 000 g · mol^?1), comprising of either low molecular weight poly(R‐3‐hydroxybutyrate) (D‐PHB) ( = 3 900 g · mol^?1) or poly[(R‐3‐hydroxybutyrate)‐co‐(R‐3‐hydroxyvalerate)] (PHBV) ( = 238 000 g · mol^?1) with 12 mol‐% hydroxyvalerate (HV) content as a second constituent, were investigated along with the thermal properties and morphologies. After isothermal crystallization, a lowering of the melting temperature of PHB can be observed with increasing content of the second component in the blends. This behavior points towards miscibility of the constituents both in the liquid and the solid state. Crystallization kinetics was studied under isothermal and non‐isothermal conditions. The overall kinetics of isothermal crystallization was analyzed in terms of the Avrami equation. Only one crystallization peak is observed in all cases for the PHB/D‐PHB and PHB/PHBV blends under the conditions studied. This demonstrates co‐crystallization of the constituents. The addition of D‐PHB or PHBV to PHB reduces the rate of crystallization of the blends compared to that of neat PHB. The corresponding activation energies of crystallization also decrease with an increasing concentration of the second constituent. Non‐isothermal crystallization, carried out with different cooling rates held constant, is discussed in terms of a quasi‐isothermal approach. The corresponding rate constants as functions of reciprocal undercooling show Arrhenius‐like behavior in a certain range of temperatures. At sufficiently high undercooling, the rate constants of crystallization for the isothermal process exceed those reflecting non‐isothermal conditions, whereas in the limit of low undercoolings, the rate constants become similar. Ring‐banded morphologies are observed when PHB is in excess. When the respective second component is the major component, fibrous textures of the spherulites develop.

Polarized micrograph of PHB/PHBV 90/10.     

Facile Synthesis of Aqueous‐dispersible Nano‐PEDOT:PSS‐co‐MA Core/Shell Colloids Through Spray Emulsion Polymerization

This paper describes a novel spray emulsion polymerization technique for the preparation of aqueous‐dispersible nanoscale core/shell poly(3,4‐ethylenedioxythiophene) (n‐PEDOT) colloids doped with poly[(4‐styrenesulfonic acid)‐co‐(maleic acid)] (PSS‐co‐MA). Scanning electron microscopy and transmission electron microscopy images revealed that these n‐PEDOT:PSS‐co‐MA colloids possessed sharp core/shell morphologies. X‐ray diffraction and Raman spectroscopy measurements revealed semi‐crystalline morphologies and quinoid‐dominated structures for these n‐PEDOT:PSS‐co‐MA colloids. The conductivities of n‐PEDOT and n‐PEDOT:PSS‐co‐MA pellets were ca. 3.2 and 0.29 S · cm^?1, respectively, suggesting that PSS‐co‐MA acted as a shell that blocked the hopping of charges from the n‐PEDOT core to neighboring latexes. The work functions of pristine n‐PEDOT and n‐PEDOT:PSS‐co‐MA, measured using photoelectron spectroscopy, were ca. 4.7 and 5.05 eV, respectively; thus, they are close to that of indium tin oxide. The PSS‐co‐MA used in this study featured two different types of interactive functional groups, which acted as oxidative sites, dopants, and core/shell stabilizers during polymerization.

     

Effect of a Water‐Soluble Polymer on Polymer Interdiffusion in P(MMA‐co‐BA) Latex Films

We describe non‐radiative energy‐transfer experiments to measure the rates of polymer interdiffusion in P(MMA‐co‐BA) latex films formed in the presence of poly(vinyl alcohol) (PVOH). PVOH had relatively little effect on the initial efficiency of energy transfer, even when the amount of PVOH was large enough to form the continuous phase. Since Φ_ET(0) is a measure of the interfacial area between D‐ and A‐labeled cells in the film, we conclude that under these circumstances the dispersed P(MMA‐co‐BA) copolymer is in the form of clusters with many contacts between particles containing D and A labels. These large amounts of PVOH also reduce the amount of polymer diffusion that takes place when the films are annealed. When smaller amounts of PVOH are present, the effects are measurable but much smaller. In the presence of 2 to 17 wt.‐% PVOH, the polymer diffusion rate is retarded. The magnitude of the effect increases with the amount of PVOH present, and the effect is larger at 45 °C than at 63 °C. We show that the PVOH has its largest influence at the very early stages of polymer diffusion.

Schematic representation of an energy transfer experiment, which monitors polymer interdiffusion in a latex film.     

Studies on the Synthesis and Conductivity of a Novel Reactive Ladder‐Like Poly(β‐cyanoethylsilsesquioxane) and Poly[(β‐cyanoethylsilsesquioxane)‐co‐(β‐methylsilsesquioxane)]

Two novel reactive poly(β‐cyanoethylsilsesquioxane) ( CN‐T ) and poly[(β‐cyanoethylsilsesquioxane)‐co‐(β‐methylsilsesquioxane)] ( CN‐Me‐T ) have been synthesized successfully for the first time via stepwise coupling polymerization (SCP). A variety of characterization methods including FTIR, ¹H NMR, ²⁹Si NMR, X‐ray diffraction (XRD), differential scanning calorimetry (DSC) and vapor pressure osmometry (VPO) were combined to demonstrate that the structures of the title polymers possess ordered ladder‐like structures. As expected, the ionic conductivity of these polymers mixed homogeneously with lithium perchlorate reached 10^?6 S · cm^?1 at room temperature and obviously increased with the raise of temperature.

     

Synthesis of Poly[(ethylene terephthalate)‐co‐(ε‐caprolactone)]‐Poly(propylene oxide) Block Copolyester by Direct Polyesterification of Reactive Oligomers

Summary: The objective of this study was to synthesize thermoplastic elastomers by the direct copolyesterification of reactive oligomers of poly[(ethylene terephthalate)‐co‐(ε‐caprolactone)] (PET) and poly(propylene oxide) (PPO). The synthesis of hard segment oligomers was achieved in two steps. The first step consisted of the glycolysis of PET leading to α,ω‐hydroxyl functionalized oligomers. The second step corresponded to the ring opening polymerization of ε‐caprolactone onto the hydroxyl end groups of the PET oligomers. Commercially available hydroxytelechelic poly(propylene oxide) was modified to obtain carboxytelechelic poly(propylene oxide). The chemical structure of the product was investigated by ¹H NMR and size exclusion chromatography (SEC). Multiblock poly(ester‐ether) was then synthesized by polyesterification of hydroxytelechelic poly[(ethylene terephthalate)‐co‐(ε‐caprolactone)] with carboxytelechelic poly(propylene oxide) oligomers, using different catalysts and reaction conditions. The best stoichiometric ratio for the reaction was determined in order to obtain the highest possible . The chemical structure of the synthesized poly(ester‐ether) was investigated by size exclusion chromatography and ¹H NMR. The thermal and thermomechanical behavior of the synthesized poly(ester‐ether) was investigated by differential scanning calorimetry and dynamic mechanical analysis, which showed that the poly(ester‐ether) behaved as a thermoplastic elastomer. This product could also be an interesting way for chemical recycling of PET waste.

Synthesis of multiblock co‐poly(ester‐ether).     

Stereocomplex Crystallization Behavior and Physical Properties of Linear 1‐Arm, 2‐Arm,and Branched 4‐Arm Poly(L‐lactide)/Poly(D‐lactide) Blends: Effects of Chain Directional Change and Branching

For number‐average molecular weight (M _n) below 1 × 10⁴ g mol^?1, the comparison of cold crystallization temperature and spherulite growth rate and crystallinity of linear 1‐arm, 2‐arm, and branched 4‐arm poly(L ‐lactide)/poly(D ‐lactide) blends exhibits that the effects of chain directional change and branching significantly disturb stereocomplex crystallization. In contrast, the comparison of glass transition and melting temperatures of linear 1‐arm, 2‐arm, and branched 4‐arm poly(L ‐lactide)/poly(D ‐lactide) blends indicates that the effects of chain directional change and branching insignificantly alter and largely increase the segmental mobility of the blends, respectively, and the crystalline thickness of the blends is determined by M _n per one arm not by M _n and is not affected by the molecular architecture.

     

A Poly(vinyl alcohol)‐graft‐Copolyester: Synthesis of a Novel Graft Copolymer Containing Adamantane Moieties as Guest for Cyclodextrin

A novel graft copolymer is synthesized from commercially available poly(vinyl alcohol) using ring‐opening polymerization. For the polymerization reaction of novel brush‐like poly(vinyl alcohol)‐graft‐poly(?‐caprolactone‐co‐(3‐/7‐(prop‐2‐ynyl)oxepan‐2‐one) 5 Sn(Oct)₂ is used as a catalyst. The formation of the graft copolymer is confirmed by ¹H NMR, ¹³C NMR, and Fourier transform infrared (FTIR) spectroscopy. Furthermore, the modification of the novel synthesized graft copolymer via a “click” reaction to implement adamantane groups is described. The success of the “click” reaction is proven by ¹H NMR spectroscopy and visualized by decomplexation of cyclodextrin with included phenolphthalein.

     

Swelling and Mechanical Properties of a Temperature‐Sensitive Dextran Hydrogel and its Bioseparation Applications

Summary: A series of temperature‐sensitive dextran hydrogels (poly(NIPA‐co‐GMA‐Dex)) were synthesized by the copolymerization of glycidyl methacrylate‐derivatized dextran (GMA‐Dex) and N‐isopropylacrylamide (NIPA) in aqueous solution. Their swelling and mechanical properties and bioseparation behaviors were studied. It is found that poly(NIPA‐co‐GMA‐Dex) hydrogels simultaneously exhibit much better swelling and mechanical properties. The interactions between poly(NIPA‐co‐GMA‐Dex) hydrogels and sodium dodecylsulfate (SDS), Rutin, and DL ‐α‐alanine were different because of their different hydrophobic nature, polarity, and molecular structure, and obviously depend on the temperature: the mechanism is discussed. In addition, using poly(NIPA‐co‐GMA‐Dex) hydrogels as the absorbents, gel‐extraction separation experiments of dextran and BSA solutions showed that the separation ability of poly(NIPA‐co‐GMA‐Dex) hydrogels obviously increased upon reaching the LCST.

Temperature dependence of the swelling ratio of the PNIPA (▪) and poly(NIPA‐co‐GMA‐Dex) hydrogels (r = 0.2(•), 0.4 (▴), 0.5 (▾), 0.6(♦), 0.8 (+)).     

Insights into the Ring‐Expansion Polymerization of Thiiranes with 2,4‐Thiazolidinedione

The behavior of the ring‐expansion homopolymerization of 2 (phenoxymethyl)thiirane (PMT) and propylene sulfide (PS), respectively, with thiazolidine‐2,4‐dione (TZD) as a cyclic initiator is investigated. The polymerizations show steadily growing molar masses with increasing monomer conversions. In addition, reversible merging reactions between rings are observed, with up to six merged macrocycles formed. The degree of merging is strongly dependent on the initial monomer concentration, whereas temperature has only a small impact. Under optimized conditions, ring‐poly(PMT) polymer with values of M _n up to 50 250 g mol^?1 and dispersities down to 1.11 can be synthesized. DSC and ESI‐MS measurements of the novel ring‐poly(PS) prove the formation of ring polymer having topological purity above 95%.

     

Migration of Additives in Polymer Coatings: Phosphonated Additives and Poly(vinylidene chloride)‐Based Matrix

Summary: The living radical terpolymerization of vinylidene chloride (VC₂), methyl acrylate (MA), and dimethyl‐2‐methacryloxyethylphosphonate (MAPHOS) was performed at 70 °C in benzene by a reversible addition fragmentation chain transfer (RAFT) process to yield a gradient terpolymer of controlled molecular weight ( = 5 800 g · mol⁻¹, I_p = 1.53) with a molar composition of 75:14:11 (VC₂/MA/MAPHOS). Such terpolymers, hydrolyzed (phosphonic acid groups) or not, were used as polymeric additives in coating formulations based on a poly(VC₂‐co‐MA) copolymer matrix ( = 63 300 g · mol⁻¹, I_p = 1.99, VC₂/MA = 80:20 molar ratio). The formulations were spun cast on stainless steel surfaces and the coatings were observed by scanning electron microscopy (SEM) coupled with X‐ray analyses (EDX). The hydrolyzed additive was shown to both segregate and migrate towards the metal interface, leading to a preferential organization of the coating. Hence, the matrix at the air surface acts as a barrier to gas while the additive ensures adhesion at the polymer/metal interface.

SEM photograph of a section of the coating with formulation 4 [poly(VC₂‐co‐MA‐co‐MAPHOS(OH)₂) (75:14:11)].     

Flow‐Induced Orientation in Miscible Crystalline Polymer Blends of Poly(vinylidene fluoride) and Poly[(3‐hydroxybutyrate)‐co‐(3‐hydroxyvalerate)]

Oriented films of miscible polymer blends of poly(vinylidene fluoride) and poly[(3‐hydroxybutyrate)‐co‐(3‐hydroxyvalerate)] were prepared using a flow‐orientation technique. The lamellar structure and crystal orientation depended upon composition and flow temperature (T_flow). An interlamellar exclusion structure was induced in the blend flow‐oriented below 150 °C, whereas an interlamellar inclusion structure was developed above 150 °C. The crystal orientation of PHBHV was affected by the lamellar structures because the PHBHV chains crystallized in the pre‐existing crystalline morphology of PVDF. Crystallization of PHBHV was markedly restricted at lower PHBHV contents.

     

Combining ATRP of Methacrylates and ROP of L,L‐Dilactide and ε‐Caprolactone

Coupling atom transfer radical polymerization (ATRP) and coordination‐insertion ring‐opening polymerization (ROP) provided a controlled two‐step access to polymethacrylate‐graft‐polyaliphatic ester graft copolymers. In the first step, copolymerization of methyl methacrylate (MMA) and 2‐hydroxyethyl methacrylate (HEMA) was carried out at 80 °C at high MMA concentration by using ethyl 2‐bromoisobutyrate and [NiBr₂(PPh₃)₂] as initiator and catalyst, respectively. Kinetic and molar masses measurements, as well as ¹H NMR spectra analysis of the resulting poly(MMA‐co‐HEMA)s highlighted the controlled character of the radical copolymerization, while the determination of the reactivity ratios attested preferential incorporation of HEMA. The second step consisted of the ROP of ε‐caprolactone or L ,L ‐dilactide, in THF at 80 °C, promoted by tin octoate (Sn(Oct)₂) and coinitiated by poly(MMA‐co‐HEMA)s obtained in the first step. Once again, kinetic, molar mass, and ¹H NMR data demonstrated that the copolymerization was under control and started on the hydroxyl functions available on the poly(MMA‐co‐HEMA) multifunctional macroinitiator.

Comparison of the SEC traces for the poly(MMA‐co‐HEMA) macroinitiator P2 (line only), the polymethacrylate‐g‐PLA copolymer C2 (line marked by ○), and the polymethacrylate‐g‐PLA C3 (line marked by ?).     

Formation of Thermoresponsive Gold Nanoparticle/PNIPAAm Hybrids by Surface‐Initiated,Atom Transfer Radical Polymerization in Aqueous Media

Summary: We investigated the formation of thermoresponsive gold nanoparticle/poly(N‐isopropylacrylamide) (AuNP/PNIPAAm) core/shell hybrid structures by surface‐initiated, atom transfer radical polymerization (SI‐ATRP) in aqueous media and the effect of cross‐linking on the thermoresponsiveness of the AuNP/PNIPAAm hybrids. The disulfide containing an ATRP initiator was attached onto AuNPs and the monomer, NIPAAm, was polymerized from the surface of AuNPs in the absence or presence of a cross‐linker, ethylene diacrylate, in aqueous media at room temperature. The resulting brush‐type and cross‐linked AuNP/PNIPAAm hybrids were characterized by Fourier‐transform infrared spectroscopy, transmission electron microscopy, and variable temperature dynamic light scattering.

     

Synthesis and Properties of Novel Fluorinated Poly(phenylene‐co‐imide)s

A new class of high‐performance materials, fluorinated poly(phenylene‐co‐imide)s, were prepared by Ni(0)‐catalytic coupling of 2,5‐dichlorobenzophenone with fluorinated dichlorophthalimide. The synthesized copolymers have high molecular weights ( = 5.74 × 10⁴–17.3 × 10⁴ g · mol^?1), and a combination of desirable properties such as high solubility in common organic solvent, film‐forming ability, and excellent mechanical properties. The glass transition temperature (T_gs) of the copolymers was readily tuned to be between 219 and 354 °C via systematic variation of the ratio of the two comonomers. The tough polymer films, obtained by casting from solution, had tensile strength, elongation at break, and tensile modulus values in the range of 66.7–266 MPa, 2.7–13.5%, and 3.13–4.09 GPa, respectively. The oxygen permeability coefficients ( ) and permeability selectivity of oxygen to nitrogen ( ) of these copolymer membranes were in the range of 0.78–3.01 barrer [1 barrer = 10^?10 cm³ (STP) cm/(cm² · s · cmHg)] and 5.09–6.25, respectively. Consequently, these materials have shown promise as engineering plastics and gas‐separation membrane materials.

     

Extremely Color‐Stable Blue Light‐Emitting Polymers Based on Alternating 2,7‐Fluorene‐co‐3,9‐carbazole Copolymer

Novel alternating 2,7‐fluorene‐co‐3,9‐carbazole copolymer(3,9‐PFCz) was synthesized by Suzuki polycondensation between 3‐bromo‐9‐(2‐iodo‐9,9‐dioctyl‐9H‐fluoren‐7‐yl)‐9H‐carbazole and 2,7‐bis(4,4,5,5‐tetramethyl‐1,3,2‐dioxaborolan‐2‐yl)‐9,9‐dioctylfluorene. Cyclic voltammetry studies showed a higher HOMO level (?5.23 eV) than the polyfluorene homopolymer(PFO). The glass transition temperature of the copolymer (110 °C) was much higher than that of the PFO (67 °C). After the copolymer had been annealed at 200 °C for 2 h, the PL spectra showed almost no change and no aggregation‐ or oxidation‐related undesirable long‐wavelength emission has been observed. The light‐emitting diode in configuration of ITO/PEDOT/EML/CsF/Al showed a maximum external quantum efficiency of 1.54% with a luminance of 435 cd · m^?2 and the maximum brightness of 2 630 cd · m^?2 with CIE coordinate (0.17, 0.14) was achieved at 8.4 V. The device prepared in configuration of ITO/PEDOT/PVK/polymer/Ba/Al exhibits an efficient, stable blue emission; it has a turn‐on voltage of 6 V and maximum external quantum efficiency of 1.1%. The EL emission remains stable at high current density and after thermal treatment at 150 °C for 30 min. Extremely color‐stable blue emission from alternating poly[(2,7‐fluorene)‐co‐(3,9‐carbazole)] copolymer makes it a promising candidate for flat‐panel display applications.

     

Water‐Soluble Building Blocks for Terpyridine‐Containing Supramolecular Polymers: Synthesis,Complexation, and pH Stability Studies of Poly(ethylene oxide) Moieties

Poly(ethylene oxide) of various molecular weights (M _n = 3 000, 5 200, 10 000, 16 500 g · mol^?1) has been modified with terpyridine end groups as building blocks for water‐soluble metallo‐supramolecular polymers. Metallo‐supramolecular A–A homopolymers have been prepared and characterized by complexing the terpyridine units of one selected poly(ethylene oxide) (M _n = 3 000 g · mol^?1) with the following transition metal ions in their 2+ oxidation state: Fe, Ru, Co, Ni, Cu, Zn, and Cd. In addition, the stability of the supramolecular connection with respect to pH variations has been investigated.

Schematic representation of the product of poly(ethylene oxide) modification with terpyridine end groups and the metal complexation.     

Effect of Arrangement of L‐Lactide and D‐Lactide in Poly[(L‐lactide)‐co‐(D‐lactide)] on its Resistance to Hydrolysis Studied by Molecular Modeling

Molecular modeling is used to explain how the resistance of poly[(L ‐lactide)‐co‐(D ‐lactide)] to hydrolysis is affected by the percentages of L ‐ and D ‐lactide and their arrangements in blocks or random arrangements in the polymer. Previous studies on improving the hydrolysis resistance of PLA have involved forming either poly(L ‐lactide)/poly(D ‐lactide) (PLLA/PDLA) polyblends or copolymers of L ‐ and D ‐lactide. In this study, molecular modeling was used to study the hydrolysis resistance of PLA containing various arrangements of L ‐ and D ‐lactide in the polymers. PLA copolymers are found to have less resistance to hydrolysis than a PLLA/PDLA polyblend having the same percentages of L ‐ and D ‐lactide because a polyblend can form more stereocomplexes, which is the most stable structure PLA can form.

     

Click‐Chemistry: An Alternative Way to Functionalize Poly(2‐methyl‐2‐oxazoline)

CROP has been used to synthesize well‐defined POXZ with a monofunctional (iodomethane) or a bifunctional (1,3‐diiodopropane) initiator. POXZ has been functionalized with an azido group at one (α‐azido‐POXZ, = 3.58 × 10³ g · mol^?1) or both ends (α,ω‐azido‐POXZ, = 6.21 × 10³ g · mol^?1) of the macromolecular chain. The Huisgen 1,3‐dipolar cycloaddition has been investigated between azido‐POXZ and a terminal alkyne on a small or larger molecule (PEG). In each case, the click reaction has been successful and quantitative. In this way, different telechelic polymers (polymers bearing different functions such as acrylate, epoxide, or carboxylic acid) and block copolymers of POXZ and PEG have been prepared. The polymers have been characterized by means of FTIR, ¹H NMR, and SEC.

     

Aniline‐Based Disulfide/Aniline Copolymers as a High Energy‐Storage Material

Aniline‐based disulfide, 5‐amino‐1,4‐dihydrobenzo[d]‐1′,2′‐dithiadiene (DTAn), was synthesized through a new route. The DTAn/aniline copolymers [P(DTAn‐co‐An)] were prepared by chemical oxidative polymerization. The results show that the polymerization activity of the DTAn is obviously lower than that of aniline, and the degree of polymerization increases with the increasing feed ratio of aniline and oxidant dosage. The cyclic voltammograms of the copolymers indicate that intramolecular self‐catalyzed effects occurred between the conducting backbone and the S‐S side chain. The charge–discharge tests of Li/P(DTAn‐co‐An) cell show an initial specific capacity of 262 mAh · g⁻¹, which suggests that P(DTAn‐co‐An) may be a promising cathode material in secondary lithium batteries.