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.     

Functional polymers by living anionic polymerization

The application of living anionic polymerization techniques for the functionalization of polymers and block copolymers is reviewed. The attachment of functional groups to polymeric chains of predetermined lengths and narrow molecular weight distributions is described. Carboxyls, hydroxyls, amines, halogens, double bonds, and many other functional groups can be placed at one or two ends in the center or evenly spaced along polymeric chains. Subsequent transformations of the functional groups further contribute to the versatility of such treatments. General methods based on the use, as terminators, of substituted haloalkanes, as well as the addition of living polymers or their initiators to diphenylethylenes, substituted with appropriate functional groups or molecules, are discussed. Another approach, based on the living polymerization of monomers with protected functional groups, is also discussed. It has been used for the preparation of polymers and copolymers with evenly spaced functional groups. The combination of living anionic polymerization techniques with controlled radical and cationic polymerizations is also described. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2116–2133, 2002     

Precise synthesis of thermo-responsive and water-soluble star-branched polymers and star block copolymers by living anionic polymerization

A series of thermo-responsive and water-soluble 4- and 8-arm star-branched poly(2-(2′-methoxyethoxy)ethyl methacrylate) (poly(1)) with well-defined structures were synthesized by living anionic polymerization of 1, followed by a linking reaction with a core compound substituted with either four or eight benzyl bromide moieties. Furthermore, two kinds of sequentially different 4-arm star block copolymers composed of poly(1)-block-poly ((2,2-dimethyl-1,3-dioxolan-4-yl)methyl methacrylate) (poly(4)) were also synthesized by the same linking reaction of the corresponding AB or BA diblock copolymer anion with a core compound substituted with four benzyl bromide moieties. Thus, both well-defined 4-arm (AB)₄ and (BA)₄ star-block copolymers, whose A and B are poly(1) and poly(4) segments, were successfully synthesized. These star-block copolymers were quantitatively converted to the corresponding 4-arm (AC)₄ and (CA)₄ star-block copolymers with the same compositions by hydrolytic acetal cleavage of the poly(4) segment to poly(2,3-dihydroxypropyl methacrylate) (C segment). Poly(1) segments have LCST values and, on the other hand, both water-insoluble poly(4)s and water-soluble poly(2,3-dihydroxypropyl methacrylate)s are non-thermo-responsive segments. The thermo-responsive behavior of the resulting 4- and 8-arm star-branched poly(1) as well as the 4-arm (AB)₄, (BA)₄, (AC)₄, and (CA)₄ star-branched block copolymers has been extensively studied in terms of molecular weight, arm number, composition, and block sequence. As expected, such variables were observed to affect their LCST values. Interestingly, the thermo-responsive behavior of the 4-arm (AC)₄ and (CA)₄ stars was different from that of the block copolymers used as arm segments.     

Synthesis of polymers containing conjugated dienyl end-groups by means of anionic living polymerization

In order to synthesize end-functionalized polymers with conjugated dienyl groups, living polymeric anions of polystyrene and polyisoprene were allowed to react with 5-bromo-1,3-pentadiene, 1, and 7-bromo-1,3-heptadiene, 2. The reaction of polystyryl anion and/or polyisoprenyl anion with 1 gave polymers whose end-functionalities were 65–80% regardless of the reaction conditions. On the other hand, almost quantitative functionalization was achieved when a large excess amount of 2 was used as a terminator. When 1,1-diphenylalkyl anion and enolate anion derived from t-butyl methacrylate were used, the degree of end-functionality were 70–80% at best. The resulting end-functionalized polymers were characterized by size exclusion chromatography (SEC), ¹H and ¹³C-NMR and thin layer chromatography coupled with a flame ionization detector (TLC-FID). © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 3464–3472, 1999     

Synthesis and characterization of amphiphilic triblock polymers by copper mediated living radical polymerization

2-Dimethylaminoethyl methacrylate (DMAEMA) and 2-diethylaminoethyl methacrylate (DEAEMA) block copolymers have been synthesized by using poly(ethylene glycol), poly(tetrahydrofuran) (PTHF) and poly(ethylene butylenes) macroinitiators with copper mediated living radical polymerization. The use of difunctional macroinitiator gave ABA block copolymers with narrow polydispersities (PDI) and controlled number average molecular weights (M_n’s). By using DMAEMA, polymerizations proceed with excellent first order kinetics indicative of well-controlled living polymerization. Online ¹H NMR monitoring has been used to investigate the polymerization of DEAEMA. The first order kinetic plots for the polymerization of DEAMA showed two different rate regimes ascribed to an induction period which is not observed for DMAEMA. ABA triblock copolymers with DMAEMA as the A blocks and PTHF or PBD as B blocks leads to amphiphilic block copolymers with M_n’s between 22 and 24 K (PDI 1.24-1.32) which form aggregates/micelles in solution. The critical aggregation concentrations, as determined by pyrene fluorimetry, are 0.07 and 0.03 g dm⁻¹ for PTHF- and PBD-containing triblocks respectively.     

Star-shaped polymers by living cationic polymerization. VII. Amphiphilic graft polymers of vinyl ethers with hydroxyl groups: Synthesis and host–guest interaction

Amphiphilic graft polymers of vinyl ethers (VEs) ( 6 ) where each branch consists of a hydrophilic polyalcohol and a hydrophobic poly(alkyl vinyl ether) segment were prepared on the basis of living cationic polymerization, and their properties and functions were compared with the corresponding amphiphilic star-shaped polymers. In toluene at ?15°C, the HI/ZnI₂-initiated living block polymer 2 of an ester-containing VE (CH₂? CHOCH₂CH₂OCOCH₃) and isobutyl VE (IBVE) was terminated with the diethyl 2-(vinyloxy)ethylmalonate anion [ 3 ; ^ΦC(COOEt)₂CH₂CH₂OCH ? CH₂] ( 2/3 = 1/2 mole ratio) to give a macromonomer ( 4 ), H[CH₂CH(OCH₂CH₂OCOCH₃)] _m-[CH₂CH(OiBu)]_n? C(COOEt)₂CH₂CH₂OCH ? CH₂ (m = 5, n = 15; M?_n = 2600, M?_w/M?_n = 1.13, 1.10 vinyl groups/chain). Subsequently, 4 was homopolymerized with HI/ZnI₂ in toluene at ?15°C. In 3 h, 85% of 4 was consumed and a graft polymer ( 5 ) was obtained [M?_w = 15000, DP_n (for 4 ) = 6]. The apparent M?_w (10,900) of 5 by size-exclusion chromatography (SEC) is smaller than that by light scattering as well as that (18,300) by SEC of the corresponding linear polymer with the almost same molecular weight, indicating the formation of a multi-branched structure. Hydrolysis of the pendant esters in 5 gave the amphiphilic graft polymer 6 where each branch consists of a hydrophilic polyalcohol and a hydrophobic poly(IBVE) segment. The graft polymer 6 was found to interact specifically with small organic molecules (guests) with polar functional groups, and 6 differed in solubility and host-guest interaction from the corresponding star-shaped polymer. © 1993 John Wiley & Sons, Inc.     

Synthesis of functionalized asymmetric star polymers containing conductive polyacetylene segments by living anionic polymerization

Novel 3-arm ABC, 4-arm ABCD, and 5-arm ABCDE asymmetric star polymers comprising the conductive polyacetylene precursor, poly(4-methylphenyl vinyl sulfoxide) (PMePVSO), and other segments, such as polystyrene, poly(alpha-methylstyrene), poly(4-methoxystyrene), poly(4-trimethylsilylstyrene), and poly(4-methylstyrene), were synthesized by the methodology based on living anionic polymerization using DPE-functionalized polymers. This methodology involves the addition reaction of a DPE-functionalized polymer to a living anionic polymer followed by the living anionic polymerization of MePVSO initiated from the in situ formed polymer anion with two, three, or four polymer segments. The resultant asymmetric star polymers possessed predetermined molecular weights, narrow molecular weight distributions (Mw/Mn < 1.03), and desired compositions as confirmed by SEC, 1H NMR, SLS, and elemental analysis. After thermal treatment, the PMePVSO segment in the star polymer could be completely converted into a conductive polyacetylene segment, evident from TGA and elemental analysis. These asymmetric star polymers are expected to exhibit interesting solution properties and unique microphase-separated morphological suprastructures with potential applications in nanoscopic conductive materials. Moreover, this methodology can afford the target asymmetric star polymers with arm segments varying in a wide range and enables the synthesis of more complex macromolecular architectures.     

New initiator for the low-temperature polymerization of vinyl chloride

The polymerization of vinyl chloride initiated by a mixture of tetraethyllead and ammonium ceric nitrate has been studied at low temperatures. As (NH₄)₂Ce(NO₃)₆ was insoluble in vinyl chloride, methanol was added. Methanol was found to be not only a solvent for the catalyst but also to affect the polymerization reaction by complexing the ceric ions. A reaction order of ?0.4 with respect to methanol was calculated. Rate curves were shown to decrease fairly rapidly with time, suggesting a decrease of the rate of production of radicals during the polymerization. The apparent activation energy obtained from polymerizations carried out at different temperatures was 7.4 kcal./mole. A maximum in average polymerization rate on changing the ceric salt concentration was attributed to reactions of radicals with ceric ions. Orders of 1.2 with respect to (NH₄)₂Ce(NO₃)₆ and 0.9 with respect to Pb(C₂H₅)₄ were obtained. An increase in molecular weight was observed during the polymerization; this could be accounted for by the decreasing rate of production of radicals and by the transfer process involving one component of the initiator system. The results indicate that the mechanism of formation of radicals is described by the equation:      

Synthesis and characterization of optically active helical vinyl polymers via free radical polymerization

A facile synthetic route to prepare the dual‐functional molecule, 2,5‐bis(4′‐carboxyphenyl)styrene, was developed. The esterification of this compound with chiral alcohols, that is, (S)‐(+)‐sec‐butanol/(R)‐(?)‐sec‐butanol, (S)‐(+)‐sec‐octanol/(R)‐(?)‐sec‐octanol, and D ‐(+)‐menthol/L ‐(?)‐menthol, respectively, yielded three enantiomeric pairs of novel vinyl monomers, which underwent radical polymerization to obtain helical polymers with an excess screw sense. These polymers exhibited optical rotations as large as fourfold those of the corresponding monomers. Their helical conformations were quite stable as revealed by the almost unchanged chiroptical properties measured at different temperatures. The polymers with linear alkyl tails in the side‐groups formed irreversibly columnar nematic phases in melt although the corresponding monomers were not liquid crystalline. Whereas, the polymers with cyclic tails generated no mesophase. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2408–2421, 2009     

Cell culture on polymers prepared by radiation-induced polymerization of various glass-forming monomers

The growth of cells on polymers prepared by the radiation polymerization of monomethacrylate and dimethacrylate was investigated. Cell growth was affected greatly by such properties of the polymers as water content, wettability, and porosity. Growth was promoted remarkably by rinsing the polymers with warm water at 60-70 degrees C and by irradiation of polymers with an electron beam. Cell growth decreased with increasing oxyethylene length (n) in the polymerized dimethacrylate of same series, CH2C(CH3)CO(OCH2CH2)nOCOC(CH3)CH2. A decrease in the hydrophilicity of the polymer increased cell growth rate. Formation of pore structures in the polymer films also increased the cell growth.     

Block polymers of isocyanates and vinyl monomers by homogeneous anionic polymerization

The “living” polymer method was used to prepare block polymers of vinyl monomers and isocyanates at low temperatures in toluene–tetrahydrofuran mixtures. Vinyl monomers and diisocyanates, which have one hindered isocyanate group, as in 2,4-toluene diisocyanate, form block polymers which contain pendant reactive isocyanate groups. These block polymers can be crosslinked with water, diols, diamines, etc. The polymerization is apparently limited to block polymer formation, since the polyisocyanate anion is incapable of initiating the polymerization of common vinyl monomers.     

Synthesis of end‐functionalized polymers and copolymers of cyclopentadiene with vinyl ethers by cationic polymerization

A series of cyclopentadiene (CPD)‐based polymers and copolymers were synthesized by a controlled cationic polymerization of CPD. End‐functionalized poly(CPD) was synthesized with the HCl adducts [initiator = CH₃CH(OCH₂CH₂X)Cl; X = Cl ( 2a ), acetate ( 2b ), or methacrylate] of vinyl ethers carrying pendant functional substituents X in conjunction with SnCl₄ (Lewis acid as a catalyst) and n‐Bu₄NCl (as an additive) in dichloromethane at −78 °C. The system led to the controlled cationic polymerizations of CPD to give controlled α‐end‐functionalized poly(CPD)s with almost quantitative attachment of the functional groups (F_n ∼ 1). With the 2a or 2b /SnCl₄/n‐Bu₄NCl initiating systems, diblock copolymers of 2‐chloroethyl vinyl ether (CEVE) and 2‐acetoxyethyl vinyl ether with CPD were also synthesized by the sequential polymerization of CPD and these vinyl ethers. An ABA‐type triblock copolymer of CPD (A) and CEVE (B) was also prepared with a bifunctional initiator. The copolymerization of CPD and CEVE with 2a /SnCl₄/n‐Bu₄NCl afforded random copolymers with controlled molecular weights and narrow molecular weight distributions (weight‐average molecular weight/number‐average molecular weight = 1.3–1.4). © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 398–407, 2001     

Synthesis of gel type dispersion polymers via living dispersion polymerization (LDP)

A gel type disperse polystyrene/divinylbenzene (DVB) copolymer was successfully prepared in hydrocarbon via ‘living dispersion polymerization (LDP)’ method. Characterization of the dispersed polymers was performed by a combination of size-exclusion chromatographic and transmission electron microscopic analyses. Poly(t-butylstyryl)lithium with 3,5 × 10⁴ g/mol of molecular weight was used as a steric stabilizing moiety in the living dispersion polymerization. The particle size of the dispersed polymers was able to be controlled by both the mole ratio of the concentration of poly(t-butylstyryl)lithium to n-butyllithium and the amount of monomer to over 2 μm.     

Synthesis of hyperbranched polymers by self‐addition free radical vinyl polymerization of photo functional styrene

The hyperbranched polystyrenes are prepared by the self‐addition free radical vinyl polymerization of N,N‐diethylaminodithiocarbamoylmethylstyrene (DTCS). DTCS monomers play an important role in this polymerization system as an inimer that is capable of initiating living radical polymerization of the vinyl group. The compact nature of the hyperbranched macromolecules is demonstrated by viscosity measurements compared to the linear analogues.     

Physicomechanical properties of grafted polymers obtained by radiation-induced polymerization by radical and ionic mechanisms

The radiation-induced grafting of acrylonitrile, 4-vinylpyridine, and styrene was carried out by both radical and ionic mechanisms. Grafted polymers with equal percentages of graft were obtained by the radical and ionic propagation of the grafted chains. The molecular weight of homopolymers has been determined. The thermomechanical properties of the graft polymers were investigated. The yield temperatures for the graft polymers obtained by ionic propagation of the grafted chains is higher than that of graft polymers obtained by a radical mechanism. This is attributed to the higher molecular weight of the grafted chains obtained by the radiation-induced grafting by the ionic mechanism. The radiation-induced grafting of polyacrylonitrile increases significantly the thermal stability of polyethylene. The differential thermal analysis shows no marked differences in properties of the polymers.     

Synthesis of polyphenylacetylene by radiation-induced polymerization in deoxycholic acid clathrate

Phenylacetylene was polymerized as inclusion compound (clathrate) inside deoxycholic acid (DOCA) crystals. The polymerization was initiated by γ radiation and a total dose of 320 kGy was employed. The resulting polyphenylacetylene (PPA) was isolated by dissolution of deoxycholic acid in boiling ethanol. PPA high polymer was accompanied by a series of phenylacetylene oligomers, which were detected by liquid chromatographic analysis (HPLC). PPA was characterized by electronic absorption spectroscopy and by FT-IR spectroscopy in comparison to a reference PPA prepared by a stereospecific catalyst. The microstructure of PPA from inclusion polymerization was highly trans type, similar to that observed on PPA prepared by bulk radiolysis. No optical activity was detected by polarimetry on PPA prepared by inclusion polymerization.The host–guest complex PPA/DOCA was studied by differential thermal analysis (DTA) and by thermogravimetry (TGA). DTA provided evidences of the host–guest complex formation from the shift of the melting point of DOCA while the TGA confirmed the identity – in terms of thermal behaviour – of the PPA from inclusion polymerization with that from stereospecific polymerization.     

Lifetime of living polymers in cationic polymerization. II. Living polymerization of isobutyl vinyl ether initiated by the hydrogen iodide/zinc halide systems

In the living cationic polymerization of isobutyl vinyl ether (IBVE) initiated by the hydrogen iodide/zinc halide (HI/ZnX₂; X = I, Br, Cl) systems, the concentration ([P^*]) of the living propagating species was determined by quenching with sodiomalonic ester ( 1 ). The quenching reaction was shown to be clean, instantaneous, and quantitative to give poly (IBVE) with a terminal malonate group from which [P^*] was obtained by ¹H-NMR spectroscopy. In the polymerizations in toluene below +25°C, [P^*] was constant and equal to the initial concentration ([HI]₀) of hydrogen iodide, independent of the type and concentrations of ZnX₂ as well as monomer conversion. At 0 and +25°C, however, the living species started decaying immediately after the complete consumption of monomer. In contrast, such a decay process was absent at ?15°C even in the absence of monomer until about an hour (depending on the conditions) after the end of polymerization. The deactivation reaction was first order in [P^*], and the lifetime (half-life) of the living species was longer at lower temperature and at lower ZnX₂ concentration. On the basis of these [P^*] and lifetime measurements, the HI/ZnX₂ systems were also compared with the HI/I₂ counterpart.