Well-defined Graft Copolymers Research Articles

Synthesis of well-defined functional PE graft copoly-mers via ATRP process

In summary, we have demonstrated a convenient yet highly efficient method for the preparation of PE-based graft copolymers via ATRP. By introducing a small amount of styrene groups into PE chains via the selective copolymerization of ethylene with 1,4-divinylbenzene catalyzed by Et(Ind)2ZrCl2/MAO, the multifunctional ATRP initiator of 1-chloroethylbenzene-containing PE was readily achieved by a quantitative hydrochlorination reaction and was shown to be very effective for the initiation of graft polymerization of MMA and styrene to prepare structurally well-defined PE-based graft copolymers.

“Living” radical graft polymerization of styrene to styrene butadiene rubber (SBR) with 2,2,6,6‐tetramethyl‐1‐piperidinyloxy (TEMPO)

AbstractWell‐defined graft copolymers with styrene butadiene rubber (SBR) backbones and polystyrene branches were synthesized by living free radical polymerization (LFRP) techniques. Thus 1‐ benzoyl‐2‐phenyl‐2‐(2′,2′,6′,6′‐tetramethyl‐piperidinyl‐1′‐oxy)ethane (BZ‐TEMPO) was synthesized and hydrolyzed to the corresponding 1‐hydroxyl derivative. This functional nitroxyl compound was coupled with brominated SBR (SBR‐Br). The resulting macroinitiator (SBR‐TEMPO) for “living” free radical polymerization was then heated in the presence of styrene for the formation of the controlled graft copolymer. 1H‐NMR and IR spectroscopy were used to investigate the structure of the polymers. Copyright © 2004 John Wiley & Sons, Ltd.

Synthesis of well-defined graft co-polymers via coupled living anionic and living ring-opening metathesis polymerisation

The synthesis of polystyrene (PS) macromonomers functionalised with a norbornene (Nbe) unit and their living ring-opening metathesis polymerisation (ROMP) to produce comb graft co-polymers is described. Macromonomers comprising of one PS chain per Nbe unit and two PS chains per Nbe unit have been synthesised with a variety of chain lengths of PS. These macromonomers have been subjected to ROMP initiated with three different catalysts and the effect of catalyst along with the effect of solvent, concentration and time on the extent and rate of macromonomer polymerisation have been studied. Molecular weight analysis of the comb graft co-polymers by triple-detection size-exclusion chromatography (SEC) with light scattering has greatly improved the ease and accuracy of interpretation of results.

New Thermoplastic Elastomers by Quasiliving Atom Transfer Free Radical Grafting

Controlled synthesis of a new thermoplastic elastomer (TPE), poly(isobutylene-g-styrene) (PIB-g-PSt) was achieved by quasiliving atom transfer radical polymerization (ATRP). A new commercially available butyl rubber containing bromobenzyl moieties was used as macroinitiator for ATRP of styrene catalyzed by CuBr/2,20-bipyridine complex. Both bulk and solution polymerization resulted in well-defined graft copolymers as indicated by analyses with 1H NMR and GPC. Phase separated morphology in these graft copolymers was found by DSC. Stress-strain analyses indicate high elongation and tensile strength for PIB-g-PSt grafts with certain composition. This new grafting process and the resulting TPE are candidates for several useful applications.

Synthesis and Surface Analysis of Siloxane-Containing Amphiphilic Graft Copolymers, Poly(2-hydroxyethyl methacrylate-g-dimethylsiloxane) and Poly(2,3-dihydroxypropyl methacrylate-g-dimethylsiloxane)

A series of novel amphiphilic graft copolymers having a hydrophilic poly(2-hydroxyethyl methacrylate) [poly(HEMA)] or water-soluble poly(2,3-dihydroxypropyl methacrylate) [poly(DHPMA)] backbone and hydrophobic poly(dimethylsiloxane) (PDMS) side chains have been synthesized to develop a model system to examine surface properties under dry and wet conditions. The direct radical copolymerization of PDMS macromer with HEMA generated graft copolymers poly(HEMA-g-DMS) with broad molecular weight distributions (MWD; Mw/Mn = 2.85−3.55). The anionic copolymerization of the same PDMS macromer with silyl-protected HEMA, namely, 2-(trimethylsiloxy)ethyl methacrylate (SiEMA), produced graft copolymers, poly(SiEMA-g-DMS). Successive hydrolysis eliminated the protecting trimethylsilyl groups in the backbone to afford amphiphilic graft copolymers poly(HEMA-g-DMS) with a narrow MWD (Mw/Mn = 1.09−1.16). For the well-defined graft copolymer with a water-soluble poly(DHPMA) backbone and hydrophobic PDMS side chains, anionic ...

Synthesis and stabilizing properties of amphipolar polyelectrolytes

A series of well-defined amphipolar block, graft and statistical copolymers based on the same polar and non-polar monomers were synthesized and investigated for their stabilizing activity against flocculation of solid particles (pigments). The copolymers were characterized and theirstabilizing efficiency was tested with the electrokinetic sonic amplitude (ESA) and the sedimentation method. The measurements revealed that both the type of the copolymer structure and the ratio of polar and non-polar structural elements in the macromolecule play an important role in the adsorption of copolymers on the surface of pigment particles and their stabilization.

Transition in Tethered Layer Thickness Induced by Concentration Changes in a Spread Film of an Amphiphilic Graft Copolymer

Three well-defined graft copolymers and a polynorbornene backbone with a poly(ethylene oxide) graft on each backbone repeat unit have been synthesized with fully hydrogenous and deuterated poly(eth...

Synthesis and Characterization of a Well-Defined Graft Copolymer Containing Fluorine Grafts by “Living”/Controlled Radical Polymerization

The well-defined graft copolymer consisting of side chains containing fluorine was synthesized by atom transfer radical polymerization (ATRP) of 2,2,3,3,4,4;5,5-octafluoropentyl acrylate (OFPA) with the copolymer of styrene and chloromethylstyrene as macro-initiato, which was first synthesized by the nitroxide-mediated copolymerization of styrene (St) and 4-chloromethylstyrene (CMS) at 130°C with benzozyl peroxide/4-hydro-TEMPO as initiator. These copolymers, i.e. P(St-co-CMS) and P(St-g-OFPA), were characterized by means of GPC, IR and 1 H NMR, respectively. The water contact angles on polystyrene films containing small amount of P(St-g-OFPA) as additive were also measured and studied.

Synthesis of Branched Polymers by Means of Living Anionic Polymerization, 7. Synthesis of Well-Defined Highly Branched Polymers and Graft Copolymers Having One Branch per Repeating Unit Using Poly(m-halomethylstyrene)s as Backbone Polymers

Well-defined poly(m-chloromethylstyrene) and poly(m-bromomethylstyrene) were prepared by the living anionic polymerization of m-(tert-butyldimethylsilyl)oxymethylstyrene and subsequent transformation reactions with BCl3 and (CH3)3SiCl/LiBr. The reaction of poly(m-chloromethylstyrene)s with 1,1-diphenylethylene (DPE) end-capped polystyryllithium proceeded very fast in the initial stage (76% of efficiency after 10 min) and reached quantitative reaction efficiency after 24 h at –40°C. The reaction of poly(m-bromomethylstyrene) with DPE end-capped polystyryllithium of molecular weight value of up to 68.8 kg/mol proceeded completely without steric hindrance of the polystyrene branch at –40°C for 168 h to afford a very high molecular weight branched polystyrene with one branch per repeating unit (Mw = 2.3 million). Well-defined graft copolymers with the same architecture were also successfully synthesized by reacting poly(m-halomethylstyrene)s with living anionic polymers of isoprene, 2-vinylpyridine, and tert-butyl methacrylate at –40°C for 168–336 h. The high compact structures of the branched polystyrenes synthesized here comparable to those of star-branched polymers were confirmed by viscosity measurement performed in toluene at 35°C.

Metallocene-Catalyzed Copolymerization of MMA with Anionically Synthesized Methacryloyl Macromonomers

Well-defined graft copolymers with poly(methyl methacrylate) backbone and poly(styrene) (PS), poly(isoprene) (PI), or poly(dimethylsiloxane) (PDMS) branches were synthesized by combining anionic and metallocene catalyzed polymerization. The synthetic strategy involves the preparation of methacryloyl macromonomers of PS, PI, and PDMS by anionic polymerization, followed by copolymerization with methyl methacrylate using the highly reactive catalytic system Cp2ZrMe2/B(C6F5)3/ZnEt2. The macromonomers and the fractionated graft copolymers were characterized by size exclusion chromatography, low-angle laser light scattering, and 1H NMR spectroscopy.

Organization of Well-Defined Amphiphilic Graft Copolymers at the Air−Water Interface

A well-defined graft copolymer with a polynorbornene backbone and poly(ethylene oxide) grafts has been spread at the air-water interface and the organization of the copolymer investigated over a wide range of surface concentration using neutron reflectometry. The data have been analyzed using both optical matrix and kinematic approximation methods to provide the dimensions of the regions occupied by the backbone, poly(ethylene oxide) grafts and the near surface water layer thickness. The backbone region has a constant thickness of ca. 5 A over the whole surface concentration range explored whereas the poly(ethylene oxide) graft layer increases in thickness monotonically over the same surface concentration range from ca. 15 to 45 A. A more detailed examination of the reflectivity due to the poly(ethylene oxide) layers suggests that it is composed of two layers, one of which has a uniform density of ethylene oxide segments with the second having a parabolic decay of segments. The exponent for the dependence of the poly(ethylene oxide) total layer thickness on the density of grafting of the water surface (σ) was 0.66, i.e., much stronger than predicted by theory for a brush like layer. The near surface water layer self-partial structure factor could not be fitted with the often used uniform layer model. Attempts to model this parameter using multiple uniform layer models or a parabolic increase in water number density could not reproduce the features observed experimentally, suggesting that the near surface water layer is organized in a more complex manner than hitherto suspected when in the presence of poly(ethylene oxide).

Well-Defined Graft Copolymers Based on the Selective Living Anionic Polymerization of the Bifunctional Monomer 4-(Vinylphenyl)-1-butene

The anionic copolymerization of the bifunctional monomer 4-(vinylphenyl)-1-butene (VSt) with styrene (St) was carried out in a mixture of toluene and tetrahydrofuran (THF), using n-BuLi as initiator, at −40 °C. During this process, the styrene type CC bond of VSt was selectively polymerized, and the other one in its butenyl moiety remained unchanged. The molecular weight and the composition of the resulting copolymer could be well-controlled, and its molecular weight distribution was very narrow (Mw/Mn = 1.03−1.04). The unreacted butenyl groups of the VSt units were further reacted with chlorodimethylsilane, generating another functional copolymer with reactive chlorodimethylbutylsilyl side chains. This functional polymer was used as a backbone polymer and reacted with the anionic living polymers of St, isoprene (Is), or methyl methacrylate (MMA). This coupling reaction resulted in the formation of well-defined graft (co)polymers with a poly(St) backbone and either poly(St) or poly(Is) or poly(MMA) side c...

Well-defined graft copolymers containing a poly(methacrylate) backbone and functional or block poly(vinyl ether) side chains

The anionic random copolymerization of methyl methacrylate (MMA) and 2-(1-acetoxyethoxy)ethyl methacrylate (AEEMA) was carried out using 1,1-diphenylhexyllithium (DPHL) as initiator, in the presence of LiCI ([LiCl]/[DPHL] 0 = 2), in tetrahydrofuran (THF), at -60°C. The resulting polymer, poly-(MMA-co-AEEMA), has a controlled molecular weight and a narrow molecular weight distribution (M w /M n = 1.05 ∼ 1.09). Without quenching, toluene, EtAlCl 2 and a functional monomer [2-acetoxyethyl vinyl ether (AcVE), 2-chloroethyl vinyl ether (CIVE) or 2-vinyloxyethyl methacrylate (VEMA)] were introduced into the above THF solution of the copolymer at 20°C. Every side chain of AEEMA unit of poly(MMA-co-AEEMA) was activated by EtAlCl 2 to induce the cationic polymerization of the functional monomer. THF, which was used as solvent in the preparation of the copolymer of MMA and AEEMA, acted as a Lewis base in the latter cationic polymerization, thus stabilizing the propagating site. By using this procedure, a controlled cationic polymerization of a functional monomer was achieved and a well-defined graft copolymer with functional side chains was obtained. Instead of a single functional monomer, the simultaneous addition of isobutyl vinyl ether (IBVE) and AcVE, CIVE or VEMA during the second step cationic polymerization process generated a graft copolymer with random copolymer side chains. Furthermore, a graft copolymer with block side chains could also be prepared by performing a block copolymerization during the second cationic grafting step by adding sequentially AcVE (CIVE or VEMA) and IBVE or vice versa. Every graft copolymer thus obtained possessed a high purity, controlled graft number and molecular weight as well as a narrow molecular weight distribution (M w /M n = 1.12 ∼ 1.25).

Synthesis of well-defined graft copolymers via coupled living anionic polymerization and living ROMP

Well-characterized polystyrene macromonomers containing a norbornene unit at the chain end were prepared by capping living polystyrene with exo-5-norbornene-2-carbonyl chloride. The macromonomers were then ring opened polymerized using well-defined Schrock molybdenum initiators, Mo(N-2,6-i-Pr 2C 6H 3)(OCMe 3) 2(CHR) where R is CMe 3 or CMe 2Ph, to produce well-defined graft copolymers. Well-characterized graft copolymers with polystyryl grafts of average degrees of polymerization 15, 22, 35, 50, 100 and 130 were successfully prepared. Ring opening metathesis polymerization (ROMP) of macromonomers with a molecular weight of 1550 ( DP=13 ) goes to completion at a macromonomer:initiator molar ratio of 200:1. Ring opening metathesis polymerization of macromonomers with molecular weights of 3500 and 4900 ( DP s of 32 and 46, respectively) also goes to completion even at comparatively high macromonomer:initiator molar ratios of 100:1. This produces relatively long polynorbornene backbone chains with relatively short polystyrene grafts. On the other hand, macromonomers with number average molecular weights of 10 200 and 13 200 ( DP s of 96 and 127) are completely polymerized only up to macromonomer:initiator molar ratios of 20 and 10:1, respectively. Beyond this stage polymerization stops without destruction of the living chain ends before complete consumption of macromonomers, giving short polynorbornene backbone chains with relatively long polystyrene grafts.

Synthesis of graft copolymer by coupling reaction of living poly(methyl methacrylate) with bromomethylated polystyrene

A novel, well-defined graft copolymer (polystyrene (PS)-g-poly(metthyl methacrylate) (PMMA)) with control over the length of both the backbone and the side chain was synthesized by the coupling reaction living PMMA with bromomethylated PS. The backbone polymer was prepared by the anionic polymerization of styrene with n-butyllithium followed by bromomethylation using C 8H 17OCH 2Br/SnCl 4. The living PMMA was prepared by the group transfer polymerization of MMA. Graft copolymers with a narrow molecular weight distribution, D = 1.2 ∼ 1.4 at an M¯ n of around 3 × 10 4−7 × 10 4 were obtained. The reactivity of the bromomethylated PS and the living PMMA decreased with increase in their molecular weight; the favoured reaction temperature was −20°C. Characterization of the product was performed by methods including 1H n.m.r., g.p.c. and d.s.c.. Compared with the homopolymers PS and PMMA, the copolymer had a lower glass transition temperature.

Well-defined graft copolymers via coupled living anionic and living ring opening metathesis polymerisation

The synthesis of macromonomers via the reaction of living polystyrene capped with propylene oxide with bicyclo[2.2.1]hept-5-ene-2,3- trans-dicarbonyl chloride and living ROMP of the macromonomers using well-defined Schrock molybdenum initiator to produce well-characterised graft copolymers is described. The scaling up of the ROMP of the macromonomers of different molecular weights revealed the presence of an experimental limit to the length of polynorbornene backbone chain and to the length of the polystyrene graft. It is found that as the length of polystyrene graft in the macromonomer is increased the length of polynorbornene backbone chain in the graft copolymer is decreased an observation ascribed due to steric hindrance. The ROMP of macromonomers of different molecular weight has been shown to be living allowing the synthesis of tapered and block copolymers.

Synthesis, Characterization, and Morphology of Model Graft Copolymers with Trifunctional Branch Points

Well-defined graft copolymers with polyisoprene backbones and polystyrene branches, having trifunctional branch points, of the type S2IS2 (H-shaped) and (SI)I(SI) (π-shaped) were synthesized by anionic polymerization high-vacuum techniques. The synthetic strategy involves the preparation of the outer parts of the molecules, carrying one reactive Si−Cl bond, followed by coupling with difunctional living poly(isoprenyllithium) chains. In this way, the number and placement of the branches can be precisely controlled. Molecular characterization of the fractionated samples by size exclusion chromatography with UV and RI detection, membrane osmometry, low-angle laser light scattering, and 1H-NMR spectroscopy confirmed that the materials exhibit narrow molecular weight distributions and low compositional heterogeneity. The strongly microphase-separated morphologies of these two samples were characterized using TEM and SAXS. The π architecture with a PS volume fraction of 0.21 was found to form body-centered cubic spheres, while the H architecture with a PI volume fraction of 0.64 was found to form a lamellar morphology. The observed morphology for these architectures was rationalized by formally dividing the π and H architectures into component simple (single) graft block copolymers which were mapped onto Milner's morphology diagram for simple graft copolymers.

Synthesis of well-defined all-acrylic graft copolymers

Well defined all-acrylic graft copolymers have been synthesized using the macromonomer technique. Poly(methyl methacrylate) (PMMA) macromonomers of controlled molecular weight and narrow molecular weight distribution have been synthesized by group transfer polymerization (GTP) using a protected hydroxyl functional initiator. These macromonomers were quantitatively functionalized with a polymerizable acrylic and group and copolymerized under free radical conditions with 2-ethylhexyl acrylate (2EHA) to form the desired well defined graft copolymers in high yields. The macromonomers and the copolymers have been characterized by a variety of spectroscopic, chromatographic and thermal analysis methods. Transparent, multiphase materials with glass transition temperature (Tg) values of approximately -65 °C and 115 °C were obtained. The reaction conditions necessary to generate these materials most effectively have also been investigated and are described herein.

Living Polymers in Ionic and Radical Polymerizations: Recent Developments

Abstract The discovery of living polymers, that is, assemblies of polymer molecules formed by anionic polymerization which may grow without chain-breaking reaction and may react subsequently with other monomers and various reagents through their end-groups, has led to great progress in the knowledge of the mechanism of anionic polymerization and to the synthesis of a large variety of well-defined block copolymers, graft co-polymers, and polymers with functionalized end-groups. Since only a limited number of the current monomers are polymerizable by an anionic mechanism, many attempts have been made to obtain similar results by polymerizing other monomers by cationic, radical, and Ziegler polymerization. Systems making it possible to work at temperatures higher than those used for many anionic and most cationic polymerizations would be particularly interesting.

構造が規制された分岐高分子の合成と物性

構造が規制された分岐高分子の合成と物性