Multifunctional Coupling Agents Research Articles

Study on new polymer crosslinking agents and their functional hydrogels

Functional hydrogels have been used in various fields, but their development might be limited due to the finite variety of crosslinking agents, complicated functional monomer design and synthesis. To address these issues, a new series of polyamino acid-based multifunctional coupling agents, polyaspartic hydrazide-co-aspartic acid polymers (PHAs), were synthesized through a very simple ring-opening reaction in a short time. The structures of these polymers with gradient content of acylhydrazine and carboxyl groups were characterized through 1H NMR and FT-IR. The molecular weight of PHAs and the content of acylhydrazine and carboxyl groups were tested through GPC and colloidal titration method, respectively. By crosslinking between acylhydrazine groups of PHA crosslinkers and carbonyl of diacetone acrylamide (DAAM), DAPHA hydrogels with different PHA structures and contents were prepared from acrylamide (AAM), DAAM and PHA crosslinkers in a one-step reaction. Furthermore, through coordination between pendant carboxyl of PHAs and metal cations, DAPHA-Fe3+ hydrogels were prepared by soaking DAPHA hydrogels in ferric chloride solution. And the structures and mechanical properties of both DAPHA and DAPHA-Fe3+ hydrogels were investigated. Moreover, taking advantage of the complexation and dissociation of DAPHA hydrogel with Fe3+, their shape memory properties were investigated. Finally, magnetic DAPHA-Fe3O4 hydrogels were prepared through in-situ precipitation method, and their magnetism has been studied.

Synthesis of multifunctional coupling agents and their selective reactions with hydroxy and amino groups in the melt

Three new coupling agents with different numbers of N-acyl lactam and 4H-3,1-benzoxazin-4-one groups were synthesized. A selective stepwise conversion of the coupling agents with 1-dodecanol and 1-dodecylamine was demonstrated by means of solvent-free model reactions in melt at 195 and 210 °C, respectively. These coupling agents are regarded as potential cores for the synthesis of novel star-like compounds and polymers with defined arms varying in type and lengths.

Ethoxysilyl-modified hyperbranched polyesters as mulitfunctional coupling agents for epoxy-silica hybrid coatings

Partially ethoxysilyl-modified hyperbranched aliphatic–aromatic polyesters (HBPs) were effectively used as toughening as well as multi-site coupling agents in the preparation of organic–inorganic UV-thermal dual-cured epoxy/TEOS coatings. Through chain transfer reaction of the phenolic terminal units of the HBPs effective incorporation in the epoxy resin is achieved in the photo-initiated cationic polymerization whereas the ethoxysilane groups allow effective formation of a strongly interconnected inorganic–organics network during the in-situ sol-gel process with TEOS by binding the organic to the inorganic phase. Under those conditions, the addition of the inorganic precursor to the epoxy/HPB (20 wt%) system induced an increase of the storage modulus and more important, an improvement of the viscoelastic properties by extending the performance of the elastic modulus to higher temperatures. Thus, highly transparent hybrid coatings with enhanced thermal-mechanical and surface hardness properties resulted by the use of the partially ethoxysilyl-modified HBPs as multifunctional coupling agents.

Miktoarm star copolymers via combination of RAFT arm‐first technique and aldehyde–aminooxy click reaction

AbstractA facile synthetic pathway to miktoarm star copolymers with multiple arms has been developed by combining reversible addition–fragmentation chain transfer (RAFT) arm‐first technique and aldehyde–aminooxy “click” coupling reaction. Star polystyrene (PS) with aldehyde functionalized core was initially prepared by RAFT arm‐first technique via crosslinking of the preformed linear macro‐RAFT agents using a newly designed aldehyde‐containing divinyl compound 6,6′‐(ethane‐1,2‐diylbis(oxy))bis(3‐vinylbenzaldehyde) (EVBA). It was then used as a multifunctional coupling agent for the subsequent formation of the second generation poly(ethylene glycol) (PEG) arms via the click coupling reaction between its aldehyde groups and aminooxy‐terminated PEGs. The possible formation of PS‐PEG miktoarm star copolymer with Janus‐like segregated structure in cyclohexanone was also investigated. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3323–3330, 2010

Synthesis of Poly(N-isopropylacrylamide)−Poly(ethylene glycol) Miktoarm Star Copolymers via RAFT Polymerization and Aldehyde−Aminooxy Click Reaction and Their Thermoinduced Micellization

A facile synthetic pathway to poly(N-isopropylacrylamide) (PNIPAM)−poly(ethylene glycol) (PEG) miktoarm star copolymers with multiple arms has been developed by combining reversible addition−fragmentation chain transfer (RAFT) polymerization and aldehyde−aminooxy “click” coupling reaction. Star PNIPAM with aldehyde functionalized core was initially prepared by the RAFT arm-first technique via cross-linking of the preformed linear macro-RAFT agents using a newly designed aldehyde-containing divinyl compound 6,6′-(ethane-1,2-diylbis(oxy))bis(3-vinylbenzaldehyde) (EVBA). It was then used as a multifunctional coupling agent for the subsequent formation of the second-generation PEG arms via the click coupling reaction between its aldehyde groups and aminooxy-terminated PEGs. The thermoresponsive micellization behavior of PNIPAM−PEG miktoarm star copolymer with different PEG arm numbers in water was also investigated. Opportunities are open for thermoinduced intermolecular or intramolecular micellization of PNIPAM−PEG miktoarm star copolymers via controlling the content ratio of PNIPAM and PEG, forming multimolecular micelles and unimolecular micelles, respectively.

Synthesis and characterization of AB2-type star polymers via combination of ATRP and click chemistry

Homo/miktoarm star polymers were successfully synthesized via combination of the “arm-first” and “coupling-onto” strategies. Firstly, the multifunctional coupling agent (core), 2, 4, 6-tris(3-ethynylphenyl)-1,3,5-triazine-2,4,6-triamine (TPTTA), was synthesized. Secondly, the linear polystyrene-Cl (PS-Cl) and poly(2-(dimethylamino)ethyl methacrylate)-Br (PDMAEMA-Br) were prepared by atom transfer radical polymerization (ATRP) method. Then, the linear PS-Cl and PDMAEMA-Br chains were modified by a nucleophilic substitution reaction with sodium azide. Finally, homo/miktoarm star polymers PS3 and PS(PDMAEMA)2 were designed by click reaction between the core (TPTTA) and the arm precursor (PS-N3 or PDMAEMA-N3). The structures of the PS3, PS(PDMAEMA)2 and the precursors were all characterized by NMR, FT-IR, UV and GPC analysis. Moreover, the self-assembly behaviors of the miktoarm amphiphilic copolymer PS(PDMAEMA)2 was also investigated by transmission electron microscopy (TEM).

Multifunctional coupling agents. Part 4: Block copolymers based on amino terminated polyamide-12 and carboxy terminated poly(butylene terephthalate)

A carboxy terminated poly(butylene terephthalate) (PBT) was obtained by quantitative reaction of a hydroxy terminated PBT with succinic anhydride. Subsequent melt mixing with an amino group terminated PA12 did not result in the formation of linking groups between the components. Instead, the formation of succinimide terminal groups on the polyamide-12 (PA12) chains was observed. The same conversion in presence of a bifunctional coupling agent possessing one oxazoline and one oxazinone group yielded PA12/PBT block copolymers in high extent. DSC and microscopic measurements showed that a phase separated morphology is predominant.

Multifunctional Coupling Agents: 3. Segmented Block Copolymers Based on Carboxy-Terminated Poly(propylene oxide) and Amino-Terminated Polyamide 12

Segmented block copolymers were synthesized in melt by conversion of carboxy-terminated poly(propylene oxide) and amino-terminated PA12 with a selectively reacting bifunctional coupling agent bearing one oxazoline and one oxazinone group. The reaction was performed either in one or two steps. In the latter, it could be shown that the sequence of mixing significantly influenced the course of reaction. The structure of the linking group formed during the reaction was verified by 'H NMR spectroscopy using model compounds. DSC and TEM investigations evidenced that the block copolymers are phase separated. Domains in a size of several nanometers are found. Owing to the two phase structure, the block copolymers show ductile behavior with the tendency to elastomeric behavior. Tensile properties of the block copolymers increase with the content of PA12. Elongations at break were measured with values up to 500%.

A Probability Model of Star‐Branched Polymers Formed by Connecting Polydispersed Primary Chains Onto a Multifunctional Coupling Agent

AbstractSummary: A probability model, based on the “in‐out” recursive analysis, is developed for obtaining the average molecular weights of star polymers formed by connecting polydispersed primary chains onto a multifunctional coupling agent. The average properties and the polydispersity index of the formed star polymers can be described as a function of the reaction conversion and the average properties of the polydispersed primary chains without the knowledge of the whole distribution. The results indicate that, although PI of the resulting star polymers might increase at the intermediate conversion for the higher functionalities of the core molecules, the resulting star polymers generally have narrower molecular weight distributions at the complete conversion compared to the initial polydispersed polymer chains.A schematic illustration of the star polymer formation.magnified imageA schematic illustration of the star polymer formation.

Star Polymer Synthesis Using Hexafluoropropylene Oxide as an Efficient Multifunctional Coupling Agent

Well-defined polyisoprene three-armed star polymers (PI3) were synthesized through a combination of living anionic polymerization and an efficient coupling process using hexafluoropropylene oxide (HFPO). Anionic polymerization of isoprene followed by termination with HFPO yielded three-armed stars with narrow molecular weight distributions. Under optimized conditions, at least 97% of the chains can be coupled. Molecular characterization of the star polymers (SEC, NMR and IR spectroscopy, and MALDI-TOF mass spectrometry) gave data consistent with the star structure and proposed mechanism of formation. The effects of HFPO concentration and the molecular weight of the arm precursors on the extent of star polymer formation were investigated. End-functionalized polyisoprene stars were also prepared and have potential application as trifunctional precursors to branched block copolymers.

Multifunctional coupling agents: Synthesis and model reactions

AbstractNew multifunctional coupling agents with one 2‐oxazoline group, one oxazinone group, and one allyl ether group were prepared. It was shown by means of model reactions that under the conditions of reactive extrusion, the 2‐oxazoline group and the oxazinone group reacted selectively with carboxylic groups and amino groups, respectively. The allyl ether group remained unaffected under the reaction conditions chosen. As a model reaction, the conversion of the coupling agents with 11‐aminoundecanoic acid resulted in the formation of an allyloxy‐functionalized poly(ester amide). The reaction could be performed stepwise, in the course of which the reaction of the amino group proceeded at 110 °C in solution, whereas the reaction of the carboxylic group was performed in the melt at 220 °C. Furthermore, the utilization of the coupling agents for the preparation of telechelic poly(propylene glycol) with one oxazoline group and one allyl ether group on each chain end was described. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 655–667, 2003

Compatibilization of PP/EPDM Blends via a Hexa Functional Coupling Agent and Peroxide During Reactive Extrusion

Isotactic polypropylene (PP) and ethylene-propylene-methylene-norbornene terpolymer (EPDM) were blended in a counter-rotating twin screw extruder in the presence of a peroxide initiator and a new multifunctional coupling agent (hexa(allylamino)cyclotriphosphonitrile (HAP)). The effects of free radical coupling reactions on the mechanical properties and morphologies of the resultant blends were evaluated. Blends that included both HAP and peroxide displayed an increase in low temperature impact strength. Tapping-mode atomic force microscopy(AFM) of the alloys revealed enhanced dispersion of EPDM within the PP matrix when compared to the base blends.

Multifunctional Coupling Agents for Living Cationic Polymerization. 7. Synthesis of Amphiphilic Tetraarmed Star Block Polymers with α-Methylstyrene and 2-Hydroxyethyl Vinyl Ether Segments by Coupling Reactions with Tetrafunctional Silyl Enol Ether

By the polymer coupling reaction with a tetrafunctional silyl enol ether [1; C{CH2OC6H4C(OSiMe3)CH2}4], amphiphilic tetraarmed star polymers (6) with α-methylstyrene−2-hydroxyethyl vinyl ether (αMeSt−HOVE) block arm chains have been synthesized: C{CH2OC6H4COCH2−[CH(OCH2CH2OH)CH2]n−[C(CH3)(C6H5)CH2]m−}4. The synthesis consisted of the following steps: (i) the sequential living cationic polymerization of αMeSt and 2-[(tert-butyldimethylsilyl)oxy]ethyl vinyl ether (SiVE) into an αMeSt−SiVE living block copolymer (4); (ii) the coupling of four chains of 4 with the quencher 1 into a tetraarmed polymer (5); and (iii) the transformation of the poly(SiVE) segment into the poly(HOVE) chain by the fluoride-catalyzed deprotection. In step i the living polymerization was carried out at −78 °C in methylene chloride with a binary initiating system comprising tin tetrabromide and the hydrogen chloride adduct of 2-chloroethyl vinyl ether. After step iii, the tetraarmed amphiphile 6 (αMeSt/HOVE = 27/27 in n in each arm)...

Multifunctional Coupling Agents for Living Cationic Polymerization. 6. Synthesis of Multiarmed and End-Functionalized Poly(α-methylstyrene) with Multifunctional Silyl Enol Ethers

Tri- and tetraarmed polymers (3-P and 4-P) of α-methylstyrene (αMeSt) and their end-functionalized versions (12) [R4-mC{CH2OC6H4COCH2−(αMeSt)n−CHMeOCH2CH2−X}m (Me = CH3); arm number m = 3 (R = Me), 4; X = Cl, OCOMe, OCOCMe=CH2] have been synthesized by coupling reactions of living poly(αMeSt) with multifunctional silyl enol ethers [R4-mC{CH2OC6H4C(OSiMe3)CH2}m; 3, m = 3, R = Me; 4, m = 4]. The living poly(αMeSt) was prepared by living cationic polymerization in methylene chloride solvent at −78 °C with the hydrogen chloride−vinyl ether adduct [Cl−CHMe(OCH2CH2−X)] as initiator in conjunction with tin tetrabromide (SnBr4). Subsequently, the living chains were allowed to react with 3 or 4 in the presence of N-ethylpiperidine to give the target multiarmed polymers in high yield (>90%). Specifically for αMeSt, it proved crucial that N-ethylpiperidine and similar nucleophiles should be added into the living polymer solution for its efficient coupling to occur. In the end-functionalized polymers (12), each of th...

Multifunctional Coupling Agents for Living Cationic Polymerization. 5. Synthesis of Amphiphilic Tetraarmed Star Poly(vinyl ethers) by Coupling Reactions with Tetrafunctional Silyl Enol Ether

Amphiphilic tetraarmed star poly(vinyl ethers), where each arm carries alkyl (hydrophobic) and alcohol (hydrophilic) pendant groups, have been synthesized by the coupling reaction of AB-block living poly(vinyl ethers) (4; arm chain) with a tetrafunctional silyl enol ether 1, C[CH 2 OC 6 H 4 -p-C(OSiMe 3 )=CH 2 ] 4 . The living arm chaise 4 were prepared by the sequential living cationic polymerization of an alkyl vinyl ether (CH 2 =CHOR 1 ; R 1 =iBu, CH 2 CH 2 Cl) and a fuctionalized vinyl ether (CH 2 =HOCH 2 -CH 2 R 2 ; R 2 =OCOCH 3 , OSi t BuMe 2 ) with hydrogen chloride/zinc chloride initiating system in methylene chloride at -15 o C. The treatment of 4 with the silyl enol ether 1 led to tetraarmed block copolyiners 5. The yield of 5 (93-73%) depended on the structure and the polymerization sequence of the monomer pair for the arm chain 4. The best result (93% yield) was obtained with the AB-block polymer of 2-chloroethyl vinyl ether (R 1 =CH 2 CH 2 Cl; CEVE) and 2-acetoxyethyl vinyl ether (R 2 =OCOCH 3 ; AcOVE) where CEVE has polymerized first. Separate coupling experiments with the homopolymers of these vinyl ethers showed that the coupling yield was higher for monomers with less bulky pendant groups. Subsequent quantitative deprotections of the acetoxy of tert-butyldimethylsilyl groups in 5 into hydroxyl groups gave the amphiphilic tetraarmed polymers 6. By changing the polymerization sequence of the monomer pair, the hydrophilic polyalcohol segments could be placed either inside or outside the tetraarmed structure. For pairs of such inner- and outer-alcohol versions with identical segmental compositions, solubility and arm-chain conformation (by 1 H NMR) were compared

Multifunctional coupling agents for living cationic polymerization. IV. Synthesis of end‐functionalized multiarmed poly(vinyl ethers) with multifunctional silyl enol ethers

AbstractTelechelic (8) and end‐functionalized four‐arm star polymers (9) were synthesized through the coupling reactions of end‐functionalized living poly(isobutyl vinyl ether) (5; DPn ∼ 10) with the bi‐and tetrafunctional silyl enol ethers, H4‐nC[CH2OC6H4C(OSiMe3) = CH2]n (3: n = 2; 4: n = 4). The precursor polymers 5 were prepared by living cationic polymerization with functionalized initiators, CH3CH(Cl)OCH2CH2X(6), in conjunction with zinc chloride in methylene chloride at −15°C. The initiators 6 were obtained by the addition of hydrogen chloride gas to vinyl ethers bearing pendant functional groups X, including acetoxy [OC(O)CH3], styryl (OCH2C6H4‐p‐CH = CH2), and methacryloyl [OC(O)C(CH3) = CH2]. The coupling reactions with 3 and 4 in methylene chloride at −15°C for 24 h afforded the end‐functionalized multiarmed polymers (8 and 9) in high yield (>91%), where those with styryl or methacryloyl groups are new multifunctional macromonomers. © 1994 John Wiley & Sons, Inc.

Multifunctional Coupling Agents for Living Cationic Polymerization.3.Synthesis of Tri- and Tetra-Armed Poly(vinyl ethers) with Tri- and Tetrafunctional Silyl Enol Ethers

Tri- and tetrafunctional silyl enol ethers, Me 4-n C[CH 2 OC 6 H 4 C(OSiMe 3 )=CH 2 ] n (3: n=3; 4: n=4), proved efficient multifunctional coupling agent for the living polymer of isobutyl vinyl ether (IBVE) prepared by the HCl/ZnCl 2 initiating system at -15°C in CH 2 Cl 2 . The silyl enol ethers were readily synthesized by the silyl enolation of the corresponding multifunctional acetophenones. Upon the coupling reactions, the molecular weight M n of the products increased in accordance with the multiplicity of the coupling agents

Multifunctional coupling agents for living cationic polymerization. 2. Bifunctional silyl enol ethers for living poly(vinyl ethers)

Bifunctional silyl enol ethers, specifically 1,9-bis(p-[1-[(trimethylsilyl)oxy]vinyl]phenoxy)propane (5), 1,4-diethoxy-1,4-bis[(trimethylsilyl)oxy]-1,9-butadiene (6), and 2,4-bis[(trimethylsilyl)oxy]-1,9-pentadiene (7), are highly soluble and efficient bifunctional coupling agents for the living polymers of isobutyl vinyl ether (IBVE) initiated with HI/ZnCl 2 at -15°C in CH 2 Cl 2 and toluene solvents. The products are linear poly(IBVE) with molecular weights twice those of the starting living chains and with molecular weight distributions are narrow as those of the precursors

Multifunctional coupling agents for living cationic polymerization. I. Sodiomalonate anions for vinyl ethers

AbstractA series of multifunctional malonate anions, [Na⊕⊖C(COOEt)2CH2]mC6H6−m(I; m = 2–4), were examined as polymer coupling agents for the living cationic polymerization of vinyl ethers initiated with the hydrogen iodide/zinc iodide (HI/ZnI2) initiating system. The bifunctional anion (2;I, m = 2), 1,4‐[Na⊕⊖C(COOEt)2CH2]2C6H4, terminated living polymers of isobutyl vinyl ether (IBVE) (DPn = 10) almost quantitatively in toluene at −15°C to give coupled living polymers with doubled molecular weights in 96% yield; the dianion 2 was dissolved in tetrahydrofuran containing 18‐crown‐6 for maintaining the solution homogeneous. The yield of the coupled polymers was increased with shorter living chains or in less polar solvents. Also by coupling via 2, ABA block copolymers were obtained from living AB block polymers of IBVE and an ester‐functionalized vinyl ether (CH2CHOCH2CH2OCOCH3). Coupling of living poly(IBVE) with the trifunctional anion (3; I, m = 3) led to tri‐armed polymers in 56% yield, whereas with the tetrafunctional version (4; I, m = 4), only three out of the four anions reacted to give another tri‐armed polymer in 85% yield. © 1993 John Wiley & Sons, Inc.

Organic polymeric coatings for silica fibers. I. UV‐curing epoxy acrylate (V1F)

AbstractCoated optical fibers (∼100 μm) were prepared exhibiting fracture strengths in excess of 750 ksi (5.3 GN/m2) for lengths up to 100 meters. To achieve this we have developed a novel coating and coating application process. The coating is an epoxy acrylate, cured by UV irradiation, which may contain a multifunctional silane coupling agent. The coating liquid was applied to the fiber prior to solidification by an applicator, which facilitates centering of the fiber in the coating. Our coating system offers advantages in that there is no solvent to remove, thereby avoiding possible surface “corrosion” of the glass fiber. The reasonably low viscosity of the coating formulation allows for the extensive wetting of the fiber surface irregularities prior to solidification.