Synthesis of a novel centipede-like copolymer of styrene and methyl methacrylate

A well-defined,A2B-type,centipede-like copolymer of styrene and methyl methacrylate(PS-PS-PMMA) was synthesized by the combination of living anionic polymerization and atom transfer radical polym-erization(ATRP) . The synthetic approach involves the coupling reaction of polystyrene(PS) backbone bearing 1,1-diphenylethene(DPE) pendant groups,produced by ATRP and Wittig reaction,with living polystyryllithium(PSLi) ,and subsequent polymerization of the resulting 1,1-diphenylmethyl anions with methy methacrylate. The centipede-like copolymer was characterized by 1H NMR,IR,SEC,SLS,and DSC measurements.     

Synthesis of heteroarm star polymers comprising poly(4-methylphenyl vinyl sulfoxide) segment by living anionic polymerization

<正>A series of 3-arm ABC and AA'B and 4-arm ABCD,AA'BC and AA′A″B heteroarm star polymers comprising one poly(4-methylphenyl vinyl sulfoxide) segment and other segments such as polystyrene,poly(α-methylstyrene), poly(4-methoxystyrene) and poly(4-trimethylsilylstyrene) were synthesized by living anionic polymerization based on diphenylethylene(DPE) chemistry.The DPE-functionalized polymers were synthesized by iterative methodology,and the objective star polymers were prepared by two distinct methodologies based on anionic polymerization using DPE-functionalized polymers.The first methodology involves an addition reaction of living anionic polymer with excess DPE-functionalized polymer and a subsequent living anionic polymerization of 4-methylphenyl vinyl sulfoxide(MePVSO) initiated from the in situ formed polymer anion with two or three polymer segments.The second methodology comprises an addition reaction of DPE-functionalized polymer with excess sec-BuLi and a following anionic polymerization of MePVSO initiated from the in situ formed polymer anion and 3-methyl-1,1-diphenylpentyl anion as well.Both approaches could afford the target heteroarm star polymers with predetermined molecular weight,narrow molecular weight distribution (M_w/M_n1.03) and desired composition,evidenced by SEC,~1H-NMR and SLS analyses.These polymers can be used as model polymers to investigate structure-property relationships in heteroarm star polymers.     

Synthesis of Isotactic Polystyrene-block-Polyethylene by the Combination of Sequential Monomer Addition and Hydrogenation of 1,4-Trans-polybutadiene Block

Herein, we demonstrate the synthesis of a well-defined diblock copolymer consisting of isotactic polystyrene(iPS) and linear polyethylene, isotactic polystyrene-block-polyethylene(iPS-b-PE),by the combination ofsequential monomer addition and hydrogenation. Isospecific living polymerization of styrene and living trans-1,4-polymerization of 1,3-butadienewere catalyzed by 1,4-dithiabutandiyl-2,2′-bis(6-cumenyl-4-methylphenoxy) titanium dichloride(complex 1) activated by triisobutyl aluminum modified methylaluminoxane(MMAO) at room temperature to provide highly isotactic polystyrene(iPS) and 1,4-trans-polybutadiene(1,4-trans-PBD) with narrow molecular weight distribution. Furthermore, the iPS-b-1,4-trans-PBD was synthesized via sequential monomer addition in the presence ofcomplex 1 and MMAO.The hydrogenation of the 1,4-trans-PBD block was promoted by RuCl_2(PPh_3)_3 used as a catalyst to produce iPS-b-PE.     

Synthesis of α-Bromine- Terminated Polystyrene Macroinitiator and Its Initiation of MMA Polymerization by ATRP

In the present paper the synthesis of block copolymers via the transformation from living anionic polymerization (LAP) to atom transfer radical polymerization (ATRP) was described. Α-Bromine-terminated polystyrenes(PStBr) in the LAP step was prepared by using n-BuLi as initiator, tetrahydrofuran (THF) as the activator, α-methylstyrene (α-MeSt) as the capping group and liquid bromine (Br2) as the bromating agent. The effects of reaction conditions such as the amounts of α-MeSt, THF, and Br2 as well as molecular weight of polystyrene on the bromating efficiency (BE) and coupling extent (CE) were examined. The present results show that the yield of PStBr obtained was more than 93.8% and the coupling reaction was substantially absent. PStBr was further used as the macroinitiator in the polymerization of methyl-methacrylate(MMA) in the presence of copper(Ⅰ) halogen and 2,2-bipyridine(bpy) complexes. It was found that the molecular weight of the resulted PSt-b-PMMA increased linearly with the increase of the conversion of MMA and the polydispersity was 1.2-1.6. The structures of PStBr and P(St-b-MMA) were characterized by 1H NMR spectra.     

SYNTHESIS OF BLOCK COPOLYMER BY INTEGRATED LIVING ANIONIC POLYMERIZATION-ATOM TRANSFER RADICAL POLYMERIZATION(ATRP)*

Alpha-trichloroacetoxy terminated polystyrene oligomer (PS-CH_2CH_2OCOCCl_3) and poly-(styrene-b-butadiene)oligomer [P(S-b-B)-CH_2CH_2OCOCCl_3)] were synthesized by living anionic polymeri-zation using n-butyllithium as initiator.Then the PS-CH_2CH_2OCOCCl_3 (PS-Cl_3) or P(S-b-B)-CH_2CH_2O-COCCl_3 (PSB-Cl_3) was used as the macroinitiator in thepolymerization of (meth)acrylates in the presence of CuX/bpy. AB diblock and ABC triblock copolymers were prepared bythe integrated living anionic polymerization (LAP)-atom transfer radical polymerization (ATRP). The structures of the PSB-Cl_3 and the P(S-b-MMA) were identified by FTIR and ~1H-NMR spectrum, respectively. A new way to design blockcopolymers (the combination of LAP and ATRP) was developed.     

SYNTHESIS OF POLY(METHYL METHACRYLATE)-graft-POLYSTYRENE BY ATOM TRANSFER RADICAL POLYMERIZATION

The radical copolymerization of methyl methacrylate and 2-hydroxyethyl methacrylate was carried out via atomtransfer radical polymerization (ATRP) initiated by ethyl 2-bromoisobutyrate and catalyzed by CuBr/2,2'-bipyridinecomplex. This polymerization proceeds in a living fashion with controlled molecular weight and low polydispersity. Theobtained copolymer was esterified with 2-bromoisobutylryl bromide yielding a macroinitiator, poly(methyl methacrylate-co-2-hydroxyethyl methacrylate-co-2-(2-bromoisobutyryloxy)ethyl methacrylate), and its structure was characterized by ~1H-NMR. This macroinitiator was used for ATRP of styrene to synthesize poly(methyl methacrylate)-graft-polystyrene. Themolecular weight of graft copolymer increased with the monomer conversion, and the polydispersity remained relatively low.The individual grafted polystyrene chains were cleaved from the macroinitiator backbone by hydrolysis and the hydrolyzed product was characterized by ~1H-NMR and GPC.     

Block Copolymer Networks Composed of Poly(ε-caprolactone) and Polyethylene with Triple Shape Memory Properties

In this contribution, we reported a novel synthesis of block copolymer networks composed of poly(ε-caprolactone)(PCL) and polyethylene(PE) via the co-hydrolysis and condensation of α,ω-ditriethoxylsilane-terminated PCL and PE telechelics. First, α,ω-dihydroxylterminated PCL and PE telechelics were synthesized via the ring-opening polymerization of ε-caprolactone and the ring-opening metathesis polymerization of cyclooctene followed by hydrogenation of polycyclooctene. Both α,ω-ditriethoxylsilane-terminated PCL and PE telechelics were obtained via in situ reaction of α,ω-dihydroxyl-terminated PCL and PE telechelics with 3-isocyanatopropyltriethoxysilane. The formation of networks was evidenced by the solubility and rheological tests. It was found that the block copolymer networks were microphase-separated. The PCL and PE blocks still preserved the crystallinity. Owing to the formation of crosslinked networks, the materials displayed shape memory properties. More importantly, the combination of PCL with PE resulted that the block copolymer networks had the triple shape memory properties, which can be triggered with the melting and crystallization of PCL and PE blocks. The results reported in this work demonstrated that triple shape memory polymers could be prepared via the formation of block copolymer networks.     

Synthesis and characterization of miktoarm star copolymer of styrene and butadiene using multifunctional macromolecular initiator

A new kind of multifunctional macromolecular initiator with Sn-C bonds and polydiene arms was synthesized by living anionic polymerization.At first,polydiene-stannum chloride(PD-SnCl_3) was prepared by the reaction of n-butyl-Li(n-BuLi),stannic chloride(SnCl_4) and diene.Then PD-SnCl_3 was used to react with the dilithium initiator to prepare the multifunctional organic macromolecular initiators.The result suggested that the initiators had a remarkable yield by GPC,nearly 90%.By using these multifunction...     

A versatile nanobuilding precursor for the effective architecture of well-defined organic/inorganic hybrid via click chemistry

A novel octazido substituted nanobuilding precursor,octakis[dimethy（p-azidomethylene）siloxyl]octasilsesquioxane（ODA）, was prepared by the conventional diazo-transfer reaction of octakis[dimethy（p-chloromethylene）silyl]octasilsesquioxane（ODC） with NaN₃,and its structure was characterized by FT-IR,¹H,¹³C,²⁹Si NMR and MALDI-TOF MS,respectively.The structural rearrangement of POSS core in the synthesis strategy of ODA developed in this work was effectively prohibited in comparison with traditionary azidization process.The resultant ODA was not only soluble in common solvents such as CHCl3,THF,toluene,DMF and DMSO,but also could effectively serve as a versatile nanobuilding precursor for the architecture of well-defined organic-inorganic hybrids via click chemistry.     

Synthesis of Star-like Polybutadienes by a Combination of Living Anionic Polymerization and “Click” Coupling Method

Three-arm and four-arm star-like polybutadienes(PBds) were synthesized via the combination of living anionic polymerization and the click coupling method. Kinetic study showed that the click reaction between the azido group terminated PBd-t-N3 and the alkyne-containing multifunctional linking reagent was fast and highly efficient. All coupling reactions were fully accomplished within 40 min at 50 °C in toluene in the presence of the reducing agent Cu(0), proven by 1H-NMR, FTIR and GPC measurements. For the coupling reactions between the PBd-t-N3 polymer and dialkyne-containing compound, the final conversion of the coupled PBd-PBd polymer was ca. 97.0%. When a PBd-t-N3 polymer was reacted with trialkyne-containing or tetraalkyne-containing compound, the conversion of three-arm or four-arm PBd was around 95.5% or 87.0%, respectively. Several factors influencing the coupling efficiency were studied, including the molecular weight of the initial PBd-t-N3, arm numbers and the molar ratio of the azido group to the alkynyl group. The results indicated that the conversion of the target products would be promoted when the molecular weight of the PBd-t-N3 was low and the molar ratio of the azido to alkynyl groups was close to 1.     

Towards precise synthesis of functional polymers by iterative electropolymerization

正The controllable synthesis of polymers and macromolecules with precise structures is one of the biggest challenges in polymer chemistry [1]. Although polymers with welldefined architectures and compositions could now be prepared by various living polymerization techniques [1], it remains elusive to produce macromolecular materials with precise controls of monomer sequences and easy purification procedures.     

Preparation of amphiphilic graft copolymer with polyisoprene backbone by combination of anionic polymerization and “click” reaction

A novel graft copolymer consisting of polyisoprene backbone and hydrophilic side chain with carbamic acid ester functional group was prepared via thiol-ene"click"reaction and alcohol-isocyanate reactions.Polyisoprene was synthesized by anionic polymerization using n-butyl lithium as initiator,and the pendant hydroxyl groups were introduced by the thiol-ene reaction of mercaptoethanol with the double bond of 1,2-addition units of PI backbone in the presence of radical initiator azobisisobutyronitrile. Isocyanate end group capped poly(ethylene glycol)(mPEG-NCO) was grafted onto the PI backbone through alcoholisocyanate reaction between the pendant hydroxyl groups and isocyanate group of mPEG-NCO.The structure of the graft copolymer were characterized and confirmed by means of size-exclusion chromatography,~1H NMR and FTIR spectroscopy.     

Synthesis and characterization of in-chain silyl-hydride functional SBR and self-crosslinking elastomer

Functional in-chain silyl-hydride(Si-H) SBR copolymers of 4-vinyiphenyldimethylsilanol(VPDMS) and butadiene were synthesized by living anionic polymerization,in which active group Si-H was not lost and its content was controllable. Corresponding self-crosslinking elastomers were obtained by hydrosilation of Si-H group with vinyl bonds in chain.The copolymers and elastomers were characterized by ~1H NMR,size exclusion chromatography(SEC),Fourier transform infrared (FTIR) spectroscopy,differential scanning calorimetry(DSC),and thermogravimetry analysis(TGA) techniques.     

SYNTHESIS AND CHARACTERIZATION OF FOUR-ARMED BLOCK POLY(STYRENE-b-p-NITROPHENYL METHACRYLATE)PREPARED BY THE ATRP METHOD*

A novel tetrafunctional initiator, C [CH_2O (CH_2)_3 OOCCH(Br)CH_3]_4 (1), was synthesized through the reaction oftetraol with α-bromopropionyl chloride, and then was used as initiator of atom transfer radical polymerization (ATRP) in thepreparation of 4-armed polystyrene (PSt) with narrow polydispersity. The structure, molecular weight and molecular weightdistribution (MWD) of each arm were studied by ~1H-NMR and GPC data of hydrolyzed products of the 4-armed PSt. TheATRP of St using 1/CuBr/bpy as initiator system is of "living" character based on the following evidence: narrow MWD,constant concentration of chain radical during the polymerization, control of molecular weight by the molar ratio of monomerconsumed to 1. The 4-armed poly(St-b-p-nitrophenyl methacrylate) [poly(St-b-NPMA)] was prepared by the ATRP ofNPMA using 4-armed PSt with terminal bromine as the initiator, and characterized by FT-IR, ~1H-NMR spectra and GPCcurves. The micelles with PSt as core, and PNPMA as shell were formed by dropping DMSO into a solution of 4-armedpoly(St-b-NPMA) in DMF, as proved by laser light scatter (LLS) method.     

GRAFTING OF POLYSTYRENE ONTO A NANOMETER SILICA SURFACE BY MICROEMULSION POLYMERIZATION

The grafting of polystyrene onto a nanometer silica surface by microemulsion polymerization is described. Silicawas functionalized with 3-methacryloxypropyltrimethoxysilane coupling agent before polymerization. A mixture of ionic andnon-ionic surfactants as well as water-soluble and oil-soluble initiators were used. The effect of the amount of silica and ionicsurfactant on the graft polymerization was studied. The graft polymerization procedure for styrene was also applied to methylmethacrylate. Composite particles with a core-shell structure were obtained and the yield and grafting efficiency of monomerwere high.     

Synthesis and Luminescent Property of Polycarbazole/Polyhedral Oligomeric Silsesquioxane Nanocomposites

Polyvinylcarbazole（PVK） composites containing organic-inorganic hybrid polyhedral oligomeric silse-squioxane（POSS） PVK-POSS were prepared by free radical polymerization. POSS monomers reacted with vinylcarbazole and were completely dispersed at molecular level in PVK matrix and PVK-POSS nanocomposites display higher glass transition temperature（Tg） in comparison with neat PVK. Optical properties of PVK/POSS nanocomposites were investigated by UV-spectrum and PL-spectrum and the results show that the PVK-POSS nanoparticles have a good interface effect and improve color purity effectively. The maximum absorption wavelength bathochromically shifts gradually with the increasing of the content of POSS. The luminescent intensity becomes higher and higher with the increase of POSS content, and reaches its maximum luminescent intensity when the POSS content is 3% （mass fraction）, while some POSS-rich nanoparticles are present in matrix when contents of POSS are beyond 5%.     

A SLOW RELAXATION MODE OF POLYMER CHAINS IN A SEMIDILUTE SOLUTION

Dust-free semidilute and concentrated polystyrene(PS)solutions in different solvents were prepared by slow evaporation and in situ anionic polymerization,which removes the effects of troublesome artifacts such as dust contamination and concentration gradient.The dynamics was reexamined by a combination of static and dynamic laser light scattering.In benzene and toluene(good solvents for PS),only one fast diffusive mode of polymer chains can be observed when the concentration(c)is up to 20%,which is attri...     

SYNTHESIS AND POLYMERIZATION OF OLIGO (OXYETHYLENE) MACROMONOMER

This paper reports the synthesis of methoxyoligo (oxyethylene) methacrylate (MEO_n , n is the repeating unit number of (CH_2CH_2O) in the macromonomer), and its polymerization in different solvents. MEO_n is prepared through such two independent reactions as (1) anionic polymerization of oxirane initiated by potassium alkoxide and (2) end-capping of methoxy oligo(oxyethylene) by methacrylic group. The n value can be conveniently controlled over the range of 5 ～30 by varying the molar ratio of oxirane to initiator and the molecular weight distribution of MEO_n be narrowed by increasing reaction time only in step (1). MEO_n thus obtained shows a rapid polymerization in water and benzene respectively, and both give water-soluble polymers as long as suitable conditions are used.     

THERMOSENSITIVITY OF NARROW-DISPERSED POLY(N-n-PROPYLACRYLAMIDE) PREPARED BY ATOM TRANSFER RADICAL POLYMERIZATION

Controlled polymerization of N-n-propylacrylamide was achieved by atom transfer radical polymerization(ATRP) in a N,N-dimethylformamide-water mixture(50 vol%)at room temperature with methyl 2-chloropropinonate as initiator and CuCl/tris(2-dimethylaminoethyl)amine as the catalytic system in a ratio of 1:1:1.High molecular weight homopolymers(up to 3.7×10~4)with narrow molecular weight distribution(less than 1.2)were obtained.The living character of the polymerization was further demonstrated by self-block...     

Thioxanthene-9-thione Mediated MMA Polymerization

In the "cycloketyl radical mediated living polymerization"(CMP) process, a cycloketyl compound, [9,9′]bixanthenyl-9,9′ diol(BIXAN) was ultilized as initiator and mediator. The cycloketyl(CK) radical was used as the dormant radical to achieve the increase of molecular weight. Herein, a series of cycloketyl thioketones were synthesised by Lawesson's reagent by one step reaction with high yeild,and we found that, when a special cycloketyl thioketone compound, thioxanthene-9-thione(TXT), was added to a routine radical polymerization system, TXT could capture chain radical, and simultaneously formed an radical analogous to CK radical in structure,which could trigger the growth of polymer chains. This simple system was efficient to initiate the polymerization of methyl methacrylate(MMA) and in all cases the molecular weights increased with the increase of conversions. By the end-group analysis with 1 H-NMR and MALDI-TOF MS, it was confirmed that the P-STXT radical was used to control the polymerization. The re-initiating reactions were achieved when PMMA was used as the macro-initiator.