ε-Caprolactam polymerization in presence of polyhedral oligomeric silsesquioxanes (POSS)

Polyhedral oligomeric silsesquioxanes (POSS) have been covalently linked to polyamide 6 (PA6) chains with the aim of synthesizing hybrid organic/inorganic polymer materials. The synthesis has been achieved by in situ polymerization of ε-caprolactam (CL) in presence of increasing amounts of POSS molecules, using two polymerization mechanisms (hydrolytic and anionic). The latter method has been carried out by three different approaches, in order to get PA6 samples characterized by various morphologies and content of structural defects: (i) quasi-adiabatic bulk polymerization; (ii) isothermal bulk polymerization; (iii) quasi-isothermal suspension polymerization. The products obtained have been characterized in term of structure, morphology, thermal properties and molecular mass.     

The chemoenzymatic synthesis of AB-type diblock copolymers from a novel bifunctional initiator

A novel bifunctional initiator 2,2,2-trichloroethanol (TCE) is used for the chemoenzymatic synthesis of AB-type diblock copolymer polycaprolactone-block-polystyrene (PCL-b-PSt) by combination of two fundamentally different synthetic techniques: enzymatic ring-opening polymerization (ROP) of ε-caprolactone (ε-CL) and atom transfer radical polymerization (ATRP) of styrene (St). The kinetic study on the TCE-initiated enzymatic ROP of ε-CL in the presence of the biocatalyst Novozyme-435 was investigated. By optimization of the reaction conditions, TCE quantitatively initiated enzymatic ROP of ε-CL. Trichloromethyl-terminated PCL macromolecules prepared in this way were subsequently employed as macroinitiators in the ATRP of St using CuCl/2,2′-bipyridine as the catalyst system to afford well-defined AB-type diblock copolymers PCL-b-PSt. The kinetic analysis of ATRP indicated a ‘living’/controlled radical polymerization. The polymeric nanospheres were prepared by the precipitation method from two resulting PCL-PSt diblock copolymers with different content ratio of PSt to PCL. It was determined by DLS and AFM that two different diameter nanospheres had been obtained.     

Simultaneous synthesis and doping of poly(1,6-heptadiyne-co-dipropargyl ether) using ionic initiators

Cyclocopolymerization of 1,6-heptadiyne with dipropargyl ether was carried out under nitrogen atmosphere using KSCN, KBr and KI as initiators in N,N-dimethyl formamide. The course of polymerization was monitored through UV-Vis spectroscopy. The rate of cyclocopolymerization was determined at different polymerization conditions and the relative efficiency of different initiators was evaluated. KSCN was found to be particularly an effective initiator for the copolymerization. The resulting dark brown colour polymer exhibits good solubility in common organic solvents. ¹H-NMR, FTIR and UV-Vis spectra of poly(1,6-heptadiyne-co-dipropargyl ether) revealed that the copolymer possesses cyclic polyene units in the back bone. Doped nature of the polymer was evident from UV-Vis and FTIR spectroscopy. Thermal characteristics, conductivity and electroactivity of the copolymer were also explored.     

In situ synthesis of bone‐like hydroxyapatite/polyamide 6 nanocomposites

BACKGROUND: Polymer/hydroxyapatite (HA) nanocomposites have emerged in recent years as a new class of biomaterials that can be used as artificial bone. Compared to pure HA or HA‐based bioceramics, and metallic implants, they exhibit good plasticity, improved toughness and good mechanical compatibility with natural bone. Compared to their microcomposite counterparts and the pristine polymer matrix, they show increased tensile strength and modulus, and enhanced bioactivity. RESULTS: In this study, polyamide 6 (PA6)/nanoscale HA (n‐HA) nanocomposites were prepared via in situ hydrolytic ring‐opening polymerization of ε‐caprolactam in the presence of newly synthesized n‐HA aqueous slurry. The synthesized n‐HA, which is similar to bone apatite in chemical composition, microscopic morphology and phase composition, dispersed uniformly in the composites even if its loading was up to 60 wt%. The PA6/n‐HA composites show a similarity to natural bone in chemical composition to a certain extent. Mechanical tests show that the composites are reinforced considerably by the incorporation of needle‐like n‐HA, and the composites have mechanical properties near to those of natural bone. CONCLUSION: The PA6/n‐HA nanocomposite with high n‐HA content shows a similarity to natural bone in terms of chemistry and mechanical properties. This makes it a possible candidate for biomaterials suitable for bone repair or fixation. Copyright © 2008 Society of Chemical Industry     

One-step synthesis of α-p-vinylphenylalkyl-ω-hydroxy poly(ethylene oxide) macromonomers by anionic polymerization initiated from p-vinylphenylalkanols

ω-(p-Vinylphenyl)alkanols, including methanol, ethanol, propanol, pentanol, and hexanol, have been partially alkoxidated with potassium naphthalene to initiate anionic polymerization of ethylene oxide (EO) in order to directly prepare the corresponding α-p-vinylphenylalkyl-ω-hydroxy poly(ethylene oxide) (PEO) macromonomers. p-Vinylphenylmethanol, i.e. p-vinylbenzyl alcohol (VBA) afforded the expected well-defined macromonomer via living polymerization mechanism and the kinetics have been examined as a function of extent of potassium-alkoxidation. Other alcohols such as p-vinylphenylpropanol (VPP), -pentanol (VPPT), and -hexanol (VPH) were also successful to afford the corresponding PEO macromonomers, while p-vinylphenylethanol (VPE) alkoxide polymerized EO to give p-divinylbenzene and poly(ethylene glycol) without p-vinylphenylethoxy end group, which were supposed to form by a very facile intramolecular chain transfer of the activated oligomeric alkoxide chain end to abstract a benzylic proton of the initiating fragment.     

In situ synthesis of polyamide 6/MWNTs nanocomposites by anionic ring opening polymerization

In situ anionic ring opening polymerization is used to prepare monomer casting polyamide 6 (MCPA6)/carbon nanotubes (CNTs) nanocomposites, whereby water is used as auxiliary dispersing agent of hydroxyl functionalized multiwalled carbon nanotubes (MWNTs‐OH) and ε‐caprolactam (CL) monomer. The MWNTs‐OH were dispersed homogenously in MCPA6 matrix when being observed through transmission electron microcopy. The well dispersed MWNTs‐OH existed at the center of many radial texture phases in MCPA6 matrix. Polarizing microscope analysis showed that these radial texture phases were MCPA6 spherulitic crystallities. Differential scanning calorimetry analysis revealed that the crystallization temperature of the MCPA6/MWNTs‐OH nanocomposites had been improved by adding only 0.2 wt % MWNTs‐OH when compared with pure MCPA6. The influence of MWNTs‐OH on the thermal stability of MCPA6 under nitrogen and air environments was also investigated by thermal gravimetric analysis (TGA). © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Surface modification of monodisperse‐crosslinked polymeric microspheres using a redox initiation system

The surface modification of monodisperse‐crosslinked polymeric microspheres was carried out by introducing hydroxyl groups on the surface and utilizing the redox initiation system. The emulsions of the second monomer mixture were swollen into the monodisperse PS seed particles. The hydroxyl groups were introduced by hydrolysis of the acetate groups on the surface of microspheres. Ceric ammonium sulfate in sulfuric acid solution was employed to graft the acrylic monomer onto the polymeric microspheres. The surface characteristics of the surface‐modified particles were confirmed by FTIR, SEM, and TGA measurements. From the FE‐TEM image, a uniform coating layer was confirmed on the surface of microsphere. In DSC analysis, only an exothermal peak appeared when high content of DVB was used in the seeded polymerization, while, T_gs emerged after hydrolysis and graft polymerization using the low content of DVB in the second monomer. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 1349–1356, 2006     

Toughening of polyamide 6 with a maleic anhydride functionalized acrylonitrile–butadiene–styrene copolymer

Maleic anhydride functionalized acrylonitrile–butadiene–styrene (ABS‐g‐MA) copolymers were prepared via an emulsion polymerization process. The ABS‐g‐MA copolymers were used to toughen polyamide 6 (PA‐6). Fourier transform infrared results show that the maleic anhydride (MA) grafted onto the polybutadiene phase of acrylonitrile–butadiene–styrene (ABS). Rheological testing identified chemical reactions between PA‐6 and ABS‐g‐MA. Transmission electron microscopy and scanning electron microscopy displayed the compatibilization reactions between MA of ABS‐g‐MA and the amine and/or amide groups of PA‐6 chain ends, which improved the disperse morphology of the ABS‐g‐MA copolymers in the PA‐6 matrix. The blends compatibilized with ABS‐g‐MA exhibited notched impact strengths of more than 900 J/m. A 1 wt % concentration of MA in ABS‐g‐MA appeared sufficient to improve the impact properties and decreased the brittle–ductile transition temperature from 50 to 10°C. Scanning electron microscopy results show that the shear yielding of the PA‐6 matrix was the major toughening mechanism. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

交联PMMA微球表面PS刷子的合成与表征

将含有双键的甲基丙烯酸-2-氨基乙酯化学锚接在交联聚甲基丙烯酸甲酯微球表面,然后用过氧化苯甲酰引发苯乙烯发生氮氧调控自由基原位接枝聚合反应,将聚苯乙烯接枝在交联聚甲基丙烯酸甲酯微球表面,制备了PS刷子层.用凝胶渗透色谱和红外光谱对所合成交联聚苯乙烯接枝聚甲基丙烯酸乙酯共聚物进行了表征,实验结果显示：在2,2,6,6-四甲基哌啶-1-氧自由基存在下,苯乙烯的聚合反应为＂活性＂自由基聚合,所得到的聚苯乙烯分子量分布在1.13～1.28范围,分子量随聚合时间的延长而增大（7 000～68 000 g/mol）.接枝聚合物红外光谱显示聚苯乙烯被接枝到了交联聚甲基丙烯酸甲酯微球表面.AFM 表征显示交联聚甲基丙烯酸甲酯微球尺寸在0.3～1.6 μm 范围.     

New crosslinked polymer from a rapid polymerization of acrylic acid with triaziridine‐containing compound

A triaziridine containing compound, trimethylolpropane tris(1‐aziridinepropionate) (TMPTA‐AZ), is prepared from a Michael addition of aziridine (AZ) with trimethylolpropane triacrylate (TMPTA). A rapid polymerization of acrylic acid (AA) with TMPTA‐AZ occurred at ambient temperature without catalyst. This polymerization process involves three subsequent reactions are proposed: (1) An exothermic neutralization takes place between AA and TMPTA‐AZ. (2) That neutralization heat triggers AZ ring‐opening reaction and that carboxyl group (of AA) plays as a nucleophile and results in an amino ester bond formation. (3) A final crosslinked polymer is obtained from that amino group reacts with its acrylic double bond via an intermolecular Michael addition reaction. These new crosslinked polymers with various performance properties are obtained from a mixture of AA and TMPTA‐AZ in different ratios and post‐heating. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 809–815, 2007     

Lipase-catalyzed synthesis of poly-l-lactide using supercritical carbon dioxide

The present work shows that the enzyme mediated ring-opening polymerization of l-lactide at 65 °C can be achieved using supercritical carbon dioxide. It is reported a biphasic media system where the supercritical phase coexists with a liquid organic phase, which is mainly composed of melted monomer, wherein the growing poly-l-lactide chains are soluble. The immobilized lipase B from Candida antartica was used as the biocatalyst. The results indicated that semi-crystalline polymers with a molecular weight (M_w) up to 12,900 g mol⁻¹ can be attained and that the monomer conversion is related to the biocatalyst concentration and its initial water activity (a_wi). Experiments carried out with denatured enzyme gave no monomer conversion which confirms that the enzymatic mechanism is only involved in our system.     

Reducing active layer thickness of polyamide composite membranes using a covalent organic framework interlayer in interfacial polymerization

Polyamide(PA)-based thin-film composite membranes exhibit enormous potential in water purification, owing to their facile fabrication, decent performance and desirable stability. However, the thick PA active layer with high transport resistance from the conventional interfacial polymerization hampers their applications. The controllable fabrication of a thin PA active layer is essential for high separation efficiency but still challenging. Herein,a covalent organic framework TpPa-1 interlayer was firstly deposited on a polyethersulfone(PES) substrate to reduce the thickness of PA active layer in interfacial polymerization. The abundant pores of TpPa-1 increase the local concentration of amine monomers by adsorbing piperazine molecules, while hydrogen bonds between hydrophilic groups of TpPa-1 and piperazine molecules slow down their diffusion rate. Arising from those synergetic effects, the PA active layer is effectively reduced from 200 nm to 120 nm. By optimizing TpPa-1 interlayer and PA active layer, the water flux of resultant membranes can reach 171.35 L·m~(-2)·h~(-1)·MPa~(-1), which increased by 125.4% compared with PA/PES membranes, while the rejection rates of sodium sulfate and dyes solution remained more than 90% and 99%, respectively. Our strategy may stimulate rational design of ultrathin PA-based nanofiltration membranes with high performances.     

Preparation of conductive polyphenylene sulfide/polyamide 6/multiwalled carbon nanotube composites using the slow migration rate of multiwalled carbon nanotubes from polyphenylene sulfide to polyamide 6

Conductive polyphenylene sulfide (PPS)/polyamide 6 (PA6)/multiwalled carbon nanotube (MWCNT) composites having 10–30 wt % PA6 and 1 wt % MWCNTs are prepared by melt mixing at 300°C for 8 min using a high concentration PPS/MWCNT masterbatch approach, and the migration kinetics of MWCNTs from thermodynamically unfavored PPS to favored PA6 was investigated. The morphology of the composites was investigated by field emission scanning electron microscopy and transmission electron microscopy, showing the localization of most MWCNTs in the PPS phase and at the interface, being different from the case of direct melt mixing where non‐conductive materials were obtained with most MWCNTs found in the PA6 phase and at the interface. The electrical resistivity and morphology of the materials as a function of time were investigated, showing that the conductive materials can be prepared within a mixing time of 4–16 min because of the slow migration rate of MWCNTs from PPS toward PA6, and MWCNTs can eventually migrate into the PA6 phase after a long mixing time of 30 min. The slow migration rate of MWCNTs was attributed to the high viscosity ratio of the two phases. This article shows a good example where the migration of MWCNTs was slow enough to control and can be used to prepare conductive polymer blends. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42353.     

Masterbatch production of polyamide 6‐clay compounds via continuous in situ polymerization from caprolactam and layered silicates

Mechanical properties of thermoplastic polymers can be improved by incorporation of nanoscaled layered silicates. To achieve a significant improvement, the silicates have to be well exfoliated within the polymer matrix. However, it is not always possible to produce exfoliated nanocompounds with the standard procedure of melt compounding. As an alternative to melt compounding, an in situ process for the production of polyamide 6‐nanocompounds is investigated. During the in situ production, the layered silicates are dispersed in the monomer caprolactam prior to the step of polymerization in a twin‐screw extruder, leading to an intercalation of the silicate filler. The production of a polyamide compound containing 0, 2, and 4 wt % nanoscaled silicates was successful. Young's modulus was increased by ～ 30–60%. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Controlled synthesis and characterizations of amphiphilic poly[(R,S)-3-hydroxybutyrate]-poly(ethylene glycol)-poly[(R,S)-3-hydroxybutyrate] triblock copolymers

Well-defined biodegradable amphiphilic triblock copolymers consisting of atactic poly[(R,S)-3-hydroxybutyrate] (PHB) and poly(ethylene glycol) (PEG) as the side hydrophobic block and middle hydrophilic block were synthesized via ring opening polymerization of (R,S)-β-butyrolactone from PEG macroinitiators and characterized using NMR, GPC, FT-IR, XRD, DSC and TG analyses. The controlled synthesis was made possible by the facile synthesis of pure PEG macroinitiators through a TEMPO-mediated oxidation. Constituting 40-70 wt% of the copolymer content, PHB blocks grown were amorphous while PEG formed crystalline phase when segment was sufficiently long. While hindering PEG crystallization, atactic PHB mixed well with amorphous PEG to give single T_g in all the copolymers. The copolymers exhibited two-step thermal degradation profile starting with PHB degradation from 210 to 300 °C, then PEG from 350 to 450 °C.     

A new strategy for the one-step synthesis of block copolymers through simultaneous free radical and ring opening polymerizations using a dual-functional initiator

Block copolymers are fascinating and complex materials that have been used in a range of diverse scientific and technological capacities. We demonstrate that a single one-step approach based on dual simultaneous polymerizations is a viable technique for the synthesis of a wide range of block copolymers by combining two dissimilar polymerization systems and using a dual-functional initiator. The main advantage of this methodology is that a simple, one-step, and simultaneous polymerization occurs in the bulk, which makes this process very attractive from both industrial and academic points of view. We plan to study the reaction kinetics and evaluate how well the ring opening catalyst [in this case, Sn(oct)₂] works under reverse ATRP conditions.     

Biosorption of anionic dyes from aqueous solutions using a novel magnetic nanocomposite adsorbent based on rice husk ash

This study investigated the potential use of an agricultural waste, rice husk ash, for the removal of methyl orange. The adsorbent was prepared via a simple one-pot synthesis of magnetic iron oxide nanoparticles (MIONs). The prepared magnetic nanocomposites were characterized using Fourier transform infrared, scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and vibrating sample magnetometer techniques. Bach adsorption experiments were carried out to evaluate the effects of initial dye concentration, pH and contact time as well as MION content on adsorption capacity. The mechanism of dye adsorption was well fitted to a pseudo-second-order kinetic model. Moreover, the equilibrium data fitted well with the Langmuir isotherm model.     

In situ polymerization and characterization of polyamide‐6/silica nanocomposites derived from water glass

Polyamide‐6/silica nanocomposites were prepared via an in situ polymerization route using silicic acid as the precursor of silica, which was extracted from water glass. Scanning electron microscopy observations showed that the silica particles were well dispersed in the polyamide‐6 matrix on the nanometer scale, which demonstrated that this method could effectively avoid agglomeration of the inorganic particles. The coupling agent, (γ‐aminopropyl) triethoxysilane, was added to introduce interfacial interactions between the silica and the polymer matrix, which led to an increased graft of polymer on the silica surface and made the material display higher performance. It was found that the incorporation of the inorganic component significantly increased the melt viscosity, tensile strength, Young's modulus, thermal decomposition temperature, glass transition temperature and Vicat softening temperature of the polyamide‐6 resin. The reinforcement of the silica particles was clearly demonstrated. Copyright © 2004 Society of Chemical Industry     

Investigation of tensile properties and dyeing behavior of various polypropylene/polyamide 6 blends using a mixture experimental design

Polypropylene has many advantages over other polymeric fibers such as high tensile strength, good abrasion resistance, high chemical resistance and very competitive price. However, the use of polypropylene fiber is restricted by the lack of affinity of conventional dyestuffs for this fiber. Many attempts have been made to improve the dyeability of polypropylene by various techniques. It must however, be noted that enhanced dyeability of polypropylene should not adversely impair its other properties, in particular its mechanical properties. To this end, in the present investigation, a mixture experimental design was used in order to attain an optimal region of proportions of three components namely polypropylene (PP), maleated polypropylene (polypropylene grafted with maleic anhydride (MAH-PP) as a compatibilizing agent) and polyamide 6 (PA6); where enhanced dyeability as well as retained mechanical properties would be achieved. Additionally, in order to analyze the morphology of the blends, differential scanning calorimetry (DSC) and scanning electron microscopy (SEM) were used. Finally, in order to evaluate effect of each component on fastness properties of the blends, wash, rub and light fastnesses were determined by the corresponding standard test methods.     

Preparation of a poly(L-lactide-co-caprolactone) copolymer using a novel tin(II) alkoxide initiator and its fiber processing for potential use as an absorbable monofilament surgical suture

A poly(L-lactide-co-caprolactone) copolymer, P(LL-co-CL), of composition 75:25 mol% was synthesized via the bulk ring-opening copolymerization of L-lactide and ε-caprolactone using a novel bis[tin(II) monooctoate] diethylene glycol coordination-insertion initiator, OctSn-OCH₂CH₂OCH₂CH₂O-SnOct. The P(LL-co-CL) copolymer obtained was characterized by a combination of analytical techniques, namely nuclear magnetic resonance spectroscopy, gel permeation chromatography, dilute-solution viscometry, differential scanning calorimetry, and thermogravimetric analysis. For processing into a monofilament fiber, the copolymer was melt spun with minimal draw to give a largely amorphous and unoriented as-spun fiber. The fiber's oriented semicrystalline morphology, necessary to give the required balance of mechanical properties, was then developed via a sequence of controlled offline hot-drawing and annealing steps. Depending on the final draw ratio, the fibers obtained had tensile strengths in the region of 200–400 MPa.