Living polymerization of [o-(trifluoromethyl)phenyl]acetylene by a new catalyst system,MoOCl4–Et3Al–EtOH (1 : 1 : 4)

A new MoOCl₄-based living polymerization catalyst, MoOCl₄–Et₃Al–EtOH (mole ratio 1 : 1 : 4)/anisole, has been developed. Polymerization of [o-(trifluoromethyl)phenyl]acetylene by this catalyst in anisole at 30°C yielded a polymer having very narrow molecular weight distribution (M_w/M_n = 1,02), a four-fold excess of ethanol over MoOCl₄ was necessary to attain narrow molecular weight distributions. Multistage polymerization experiments clearly showed the living nature of the polymerization, which was maintained in the temperature range of 0 to 30°C. The absolute number-average molecular weight of the polymer measured by vapor pressure osmometry could be correlated with the number-average molecular weight measured by gel permeation chromatography as follows: M_n(VPO) = 1,48 × M_n(GPC). The propagation rate constant (k_p) at 30°C is 1,5 mol·L^–1·s^–1.     

Polymers of carbonic acid, 28. SnOct2‐initiated polymerizations of trimethylene carbonate (TMC, 1,3‐dioxanone‐2)

SnOct₂ (Sn(II) 2‐ethylhexanoate) initiated polymerizations of TMC were studied either in conc. chlorobenzene solution at 80°C or in bulk at temperatures ≥ 120°C. Benzyl alcohol added as coinitiator accelerated the polymerization process and allowed a control of the number‐average molecular weight (M_n) via the monomer/coinitiator ratio (M/C). The formation of benzyl carbonate endgroups allowed in turn the determination of (M_n) via ¹H NMR endgroup analyses. Model reactions suggest that at 80°C intermediately formed Sn‐alkoxide groups play the role of the true initiator. At 140, 160 or 180°C neat SnOct₂ polymerized TMC in such a way that polyTMC having octanoate endgroups was formed. Variation of the monomer/initiator (M/I) ratio at 160°C enabled again a proper control of M_n via the M/I‐ratio and high molecular weight polyTMC was obtained. The influence of back‐biting degradation on the molecular weight was also studied at 160°C to find the optimum time‐temperature window.     

A New Series of Conjugated Platinum‐co‐Poly(p‐phenylenebutadiynylene)s Polymers: Syntheses and Photophysical Properties

An efficient route is developed to synthesize a series of platinum‐co‐poly(p‐phenylenebutadiynylene)s (Pt‐co‐PPBs) polymers by stoichiometric mixing of poly(p‐phenylenebutadiynylene)s (PPBs) and platinum bis‐phosphine dichlorides. This synthetic route involves two steps; first, oxidative coupling of diterminal phenyleneethynylenes (PEs) gives low‐molecular‐weight PPBs oligomers H? C?C? (Ph(OR)₂ ? C?C? C?C)_n ? Ph(OR)₂ ? C?CH (R = C₄H₉ 1 , R = C₈H₁₇ 2 , R = C₁₂H₂₅ 3 ) (M_n = 1000–3000, degrees of polymerization, P_n(M_n) = 4–6 ), which have bifunctional alkynyl end groups, and in the second step, these organic oligomers are allowed to react with trans‐[(PⁿBu₃)₂PtCl₂] to form newly designed Pt‐co‐PPBs (R = C₄H₉ 4 , R = C₈H₁₇ 5 , R = C₁₂H₂₅ 6 ) polymers. The yield of 4–6 varies from good (63%) to high (76%) with high molecular weights (M_n) ranging from 52 738 to 74 212, and this methodology tolerates different alkoxy substituted PPBs. These new organometallic polymers contain platinum to phenylenebutadiynylene (PB) ratio of 1:4 to 1:6 and are solution processable. Polymer 4 displays fluorescence at room temperature and fluorescence and phosphorescence at low temperature in thin film, which would be useful for studying the triplet emission in these polymers.     

Polythioethers with Controlled α,ω‐End Groups Prepared by Visible Light Induced Thiol–Ene Click Polymerization of Dithiol and Divinyl Ether with 4‐(N,N‐diphenylamino)benzaldehyde as Organocatalyst

This study reports a step‐growth click‐polymerization of 1,4‐benzenedimethane (BDMT) and diethylene glycol divinyl ether (DEGVE) with 4‐(N,N‐diphenylamino)‐benzaldehyde (DPAB) as a photoredox catalyst under irradiation of visible light. DPAB exhibits a strong UV–vis absorption at 350 nm and a strong fluorescence emission at 480 nm in anisole. There is a strong fluorescence quenching between BDMT and DPAB. The molecular weight of the polythiolether can be controlled by reaction time and monomer feed ratios. More importantly, α,ω‐dithiol and α,ω‐divinyl telechelic polythiolether oligomers are successfully synthesized by simply changing the molar ratios of BDMT to DEGVE. ¹H NMR and MALDI‐TOF MS spectra demonstrate that the oligomers have high end group fidelity. In addition, strong fluorescence is observed when the α,ω‐dithiol terminated polythiolether adds with N‐(1‐pyrenyl) maleimide, indicating that the as‐prepared polythiolether bears reactive thiol end groups. Furthermore, high molecular weight polythiolether are prepared by chain extension with reactive polythiolether oligomers as macro‐monomers. For example, α,ω‐divinyl oligomer (M_n = 2000 g mol^?1) could further react with α,ω‐dithiol oligomer (M_n = 2400 g mol^?1) to form high molecular weight polythiolether (M_n = 6000 g mol^?1).     

Polymerization of lactams, 54. Anionic polymerization of 2-pyrrolidone accelerated with CO2, part 3

Intrinsic viscosities in m-cresol and weight average molecular weights, M?_w, were measured for samples of high molecular weight poly(2-pyrrolidone) (poly ( 1 )) prepared by anionic polymerization of 2-pyrrolidone ( 1 ) accelerated with CO₂. It was proved that the earlier found relationship [η] = 4 · 10^?2 · M^0,77 (in cm³ · g^?1) holds for M?M_w up to 8 · 10⁵ g. mol^?1. The probable reason for the formation of poly ( 1 ) with an exceptionally high molecular weight is discussed.     

Ring‐Opening Copolymerization of 2‐Aryl‐1‐methylenecyclopropanes with Carbon Monoxide Initiated by Pd–bpy Complexes

[PdCl(Me)(bpy)] and a mixture of the complex with cocatalysts; NaBARF (BARF = [B{C₆H₃(CF₃)₂‐3,5}₄]^?), NaBF₄, AgBARF, AgBF₄, and AgOTf, catalyze the copolymerization of 2‐phenyl‐1‐methylenecyclopropane with carbon monoxide to produce a new polyketone accompanied by ring opening of the monomer. ¹H and ¹³C{¹H} NMR spectra indicate that the polymers have two isomeric repeating units in which the phenyl substituents occupy different positions. The molecular weights of the polyketones formed by the reactions with a [Pd]/[cocatalyst]/[2‐phenyl‐1‐methyleneyclopropane] ratio of 1:3:70 are in the range of M _n = 13 100–86 000. The polymer obtained by the reaction promoted by [PdCl(Me)(bpy)]/MBARF, where M = Ag or Na, shows a narrow molecular weight distribution, M _w/M _n = 1.44 and 1.59, respectively. The catalysis is effective also for the ring‐opening copolymerization of 2‐aryl‐1‐methylenecyclopropanes bearing Me and F substituents on the phenyl ring. Isotope‐labeled experiments revealed the mechanism of the polymerization, which involves a 1,2‐insertion of the monomer into the Pd–acyl bond to produce a cyclopropylmethyl palladium intermediate, and subsequent β‐alkyl elimination to give the Pd–alkyl complex.

     

Herstellung,charakterisierung und lösungseigenschaften von einheitlichen styrol-α-methylstyrol block-copolymeren

An improved anionic polymerization technique for the preparation of highly uniform styrene/α-methylstyrene linear two-block copolymers is described. Three sets of samples with molecular weights M were prepared under equal experimental conditions, namely polystyrenes (2 · 10⁵ < M < 3 · 10⁶), poly(α-methylstyrene)s (7 · 10⁴ < M < 4 · 10⁶), and block copolymers (2 · 10⁵ < M < 2,5 · 10⁶). Ultracentrifugation in a density-gradient does not show any chemical heterogeneities in the block copolymers. The molecular polydispersity U = M_w/M_n–1 is U = 0,03 or less as estimated from GPC-measurements. The high molecular and chemical homogeneity of the block copolymers and the optical similarity of the two segment types yield light scattering measurements which give molecular weights M_w, radii of gyration 〈r²〉^1/2 and second virial coefficients A₂ with almost the same accuracy as in the case of homopolymers. The radii of gyration and the intrinsic viscosities of the block copolymers give no evidence for any “intramolecular phase separation” in the good solvent toluene. The coil conformation corresponds closely to that of the homopolymers.     

Beiträge zur polymerisation von 2-isopropenylnaphthalin, 3. Anionische homopolymerisation von 2-isopropenylnaphthalin

The anionic homopolymerization of 2-isoprenylnaphthalene with butyllithium in tetrahydrofuran at –78°C is described. The refractive index increment amounts to dn/dc = 0,2084 ml/g for these polymers in toluene at 25°C and wavelength λ = 436 nm. Determination of the molecular weights by light scattering yielded values between 13 000 and 270 000. The second virial coefficients also determined by light scattering measurements are comparable with the corresponding data of poly(α-methylstyrene). A calibration curve is given for gel permeation chromatography of the poly(2-isoprenylnaphthalene)s, whose polymolecularity indexes M_w/M_n lie between 1,06 and 1,2. Their intrinsic viscosity/molecular weight relationship is [η] = 1,43·10^?2 M^0,663. From ¹H NMR of the α-methyl group fractions of isotactic triads between 30 and 55% are evaluated. The glass transition temperature extrapolated to infinite molecular weight is T_g∞ = 221°C. Above 300°C fast degradation by monomer formation is observed.     

Ring-opening polymerization of lactides using heterobimetallic yttrocene complexes

Structurally characterized, chiral heterobimetallic yttrocene derivatives Li[Y(η⁵ : η¹-C₅R₄SiMe₂NCH₂CH₂OMe)₂] (R = Me, H) have been shown to be active in the controlled ring-opening polymerization of L-lactide to give poly(L -lactide)s with high molecular weights and moderately narrow molecular weight distributions (M_w/M_n < 1.50). Both transesterification and racemization appear to be less prominent. ¹H NMR spectroscopic tetrad analysis of copolymers prepared using a mixture of L - and D -lactide demonstrates the absence of any preference for one enantiomer during the polymerization.     

Long‐Chain Branched Poly(Lactide)s Based on Polycondensation of AB2‐type Macromonomers

A series of long‐chain branched poly(d‐/l ‐lactide)s is synthesized in a two‐step protocol by (1) ring‐opening polymerization of lactide and (2) subsequent condensation of the preformed AB₂ macromonomers promoted by different coupling reagents. The linear AB₂ macromonomers are prepared by Sn(Oct)₂‐catalyzed ROP of D ‐ and L ‐lactide with 2,2‐bis(hydroxymethyl)butyric acid (BHB) as an initiator. Optimization of the polymerization conditions allows for the preparation of well‐defined macromonomers (M _w/M _n = 1.09–1.30) with adjustable molecular weights (760–7200 g mol^?1). The two‐step approach of the synthesis comprises as well the coupling of these AB₂ macromonomers and hence allows precise control over the lactide chain length between the branching units in contrast to a random polycondensation.     

Grafting of Poly(2‐Oxazoline) Side Chains from Polyester Containing Oxazoline Units and Their Blends with Water Soluble Vinyl Polymers

Ternary polycondensation of thiomalic acid (TMA), adipic acid (ADA), and 1,5‐pentanediol (PD) at 80 °C proceeds to give polyester having pendent mercapto groups. After the mercapto groups are consumed quantitatively by a Michael addition with 2‐isopropenyl‐2‐oxazoline (IPOx) to create an initiation point for grafting, successive additions of methyl triflate (MeOTf) and 2‐oxazoline allow ring‐opening polymerization of 2‐oxazoline from the IPOx unit to give a graft copolymer with a M_n of 2.2 × 10⁴ ‐ 3.7 × 10⁴ and an molecular dispersity index (M_w/M_n = 1.9–2.6). The synthesized polyester‐based graft copolymer is water‐soluble and forms transparent blend films with poly(vinyl alcohol) (PVA) and poly(N‐isopropy acrylamide) (PNIPAM) using solvent cast methods. Differential scanning calorimetry measurements show that blends with PVA (<30% of the graft copolymer) show a single T_gs over the whole composition range. All scans for the blends with PNIPAM have a single T_gs that is between those of the parent polymers indicating that the graft copolymer shows excellent miscibility with PNIPAM, although the parent polyester, poly(TMA‐alt‐PD)‐co‐poly (ADA‐alt‐PD) does not exhibit such miscibility.     

Analysis of Heparan Sulfate from the Engelbreth-Holm-Swarm (EHS) Tumor

The size of the heparan sulfate chains from the Engelbreth-Holm-Swarm (EHS) tumor heparan sulfate proteoglycan (PG) was measured by several techniques in order to resolve uncertainty about their size and the chains were chemically characterized for comparison with other basement membrane heparan sulfate PGs. Heparan sulfate size was determined by gel filtration (M_r = 5.5 – 6.0 X 10⁴), by equilibrium sedimentation centrif-ugation (M_w = 6.8 × 10⁴), and by end group analysis (M_n = 7.1 × 10⁴). A higher molecular weight (HMW) (M_w = 2.13 × 10⁵) calculated from scattering measurements may reflect chain-chain interactions. Forty percent of newly synthesized chains eluted on gel filtration as a lower molecular weight (LMW) shoulder and in vivo turned over faster than the larger species.

A large heparan sulfate PG was present after 4 hours of in vivo ³⁵SO₄ labeling in both a low density form and a high density, slightly smaller form with large heparan sulfate chains (M_r ～ 8.0 × 10⁴). Heparan sulfate PG of intermediate size (K_av = 0.3–0.65, Sepharose CL-4B) and of smaller size (K_av = 0.75, CL-4B) were found predominantly as high density species. These PGs contained chains (M_r = 3.5 × 10⁴ and M_r = 1.2 × 10⁴, respectively) which were partially sensitive to chondroitinase ABC (CABC) and may include a hybrid heparan sulfate/chondroitin sulfate PG. Heparan sulfate chains, possibly intracellular degradation products, were also found.

Heparan sulfate chains were normal in N-sulfation (58% of hexosamine residues) and in iduronate content (～ 30%). N-sulfation started within two disaccharides of the linkage region. The EHS heparan sulfate was unusually low in O-sulfation (10% of the total sulfation) and no 6–0 sulfated, N-acetylated glucosamine residues adjacent to N-sulfated block regions were found.     

The effects of heavy metal ions (Cd2+, Hg2+, Pb2+, Bi3+) on histamine release from human adenoidal and cutaneous mast cells

The influence of lead (Pb[CH₃COO]₂), mercury (HgCl₂), cadmium (CdSO₄) and bismuth (BiO[ClO₄]) on the spontaneous and stimulated histamine release from human adenoidal and cutaneous mast cells was tested in the concentration range 10⁻⁸–10⁻⁴ M. Lead displayed a bell shaped dose-response relationship in adenoidal mast cells with a maximum at 10⁻⁶ M whereas in cutaneous cells only the spontaneous release was slightly enhanced at 10⁻⁴ M. Mercury induced a presumably toxic histamine release in adenoidal and cutaneous mast cells at 10⁻⁴ M. Cadmium increased the histamine release in adenoidal cells at 10⁻⁴ M but in cutaneous cells only the stimulated release (10⁻⁸–10⁻⁵ M) was affected. Bismuth inhibited the histamine release at 10⁻⁴ M in the adenoidal mast cells only. In conclusion, human adenoidal and cutaneous mast cells are affected differently by metal ions.

     

Synthesis and Enhanced Photofluorescence of Pyrazoline‐Ester Copolymers from Bisdiazoacetates and Diacrylates

Photofluorescent pyrazoline‐ester copolymer is synthesized from bisdiazoacetate and diacrylate through two tandem 1,3‐dipolar cycloadditions at room temperature. The first 1,3‐dipolar cycloaddition takes place between bisdiazoacetate and diacrylate, and produces the diazoacetate and acrylate‐terminated pyrazoline monomer that undergoes second 1,3‐dipolar cycloaddition further to form pyrazoline‐ester copolymer in excellent yield (up to 90%) with number‐average molecular weights (M_n) in the range of 6100–17900 g mol^?1. The optimized bisdiazo and dialkene are 1,4‐cyclohexanedimethyl bisdiazoacetate and 1,6‐hexanediol diacrylate, from which the pyrazoline‐ester copolymer with M_n 17900 g mol^?1 is obtained in 97% yield and the maximum emission intensity (I/N) is enhanced to be as high as 19 × 10⁴ a.u.. The pyrazoline‐ester copolymers are down/upconversion fluorescence materials, which emit 320–330 nm UV light through the excitation of both mid‐UV and visible light, and could find wide application in the optical field.     

Specific binding of 1-[3H]-O-alkyl-2-acetyl-sn-glyceryl-3-phosphoryl choline (platelet-activating factor,PAF) by human polymorphonuclear neutrophils

1-O-alkyl-2-acetyl-sn-glyceryl-3-phosphorylcholine (PAF) is a potent activator of polymorphonuclear neutrophil (PMN) aggregation, exocytosis and chemotaxis. Specific desensitization of PMN to PAF suggests a receptor-mediated interaction. The binding of 1-[³H]-O-alkyl-2-acetyl-sn-glyceryl-3-phosphorylcholine (³H-PAF) to human PMN and platelets was analysed and compared. Binding was saturable at 0.6 nM and 0.1 nM for 2×10⁶ PMN and 5×10⁷ platelets, respectively. The time course of binding at 22°C and 37°C for both cell types reached the plateau at 2 min. The averageK _d was 45.0±1.7 nM (mean ±1 SD of 4 experiments) for PMN (27.391±1381 sites for PMN) and 20.1±6.3 nM (4 experiments) for platelets (1577±461 sites for platelets). The Scatchard plot analysis revealed two distinct binding sites both on PMN and platelets: a high affinity binding site and a non-saturable binding site.This work was supported by C.N.R. Rome grant no. 81.00089.04.     

Visible Light–Induced RAFT Polymerization of Methacrylate with 4‐(N,N‐diphenylamino)benzaldehyde as Organophotoredox Catalyst and the Effect of Temperature on the Polymerization

With UV–vis absorption in the range of 270–435 nm, 4‐(N,N‐diphenylamino)benzaldehyde (DPAB) takes efficient photoreduction quench with 4‐cynao‐4‐(phenylcarbonothioylthio)pentanoic acid (CTP). The polymerization rates of methyl methacrylate (MMA) are 0.019, 0.056, and 0.102 h^?1 at 33, 40, and 50 °C, respectively, in the presence of DPAB and CTP under visible‐light irradiation. Dark reaction produces no PMMA at 50 °C for 120 h. The living feature is demonstrated by linearly increasing M_n with the monomer conversions and narrow polydispersity index (PDI), chain extension, and block polymerizations with benzyl methacrylate (BnMA) and poly(ethylene glycol) monomethyl ether methacrylate (PEGMA). With PMMA‐CTP (M_n = 6800, PDI = 1.17), chain extension gives PMMA with M_n = 15 900 and PDI = 1.15. With PMMA‐CTP (M_n = 6000, PDI = 1.21) as macro‐RAFT, PMMA‐b‐PBnMA of M_n = 12 600 (PDI = 1.44) and M_n = 18 500 (PDI = 1.31) are prepared. These results support that there is a positive synergistic effect between polymerization temperature and visible‐light irradiation on the photo‐RAFT without losing the living features.     

Polychloroalkane initiators in copper‐catalyzed atom transfer radical polymerization of (meth)acrylates

A series of polychloroalkanes CCl_nR_4‐n (n = 2, 3, or 4) was tested as initiators for atom transfer radical polymerization (ATRP) of methyl methacrylate (MMA) and methyl acrylate (MA) using CuCl/2,2′‐bipyridine as the catalyst. 2,2‐Dichloropropane and 2,2‐dichloroethanol initiate the ATRP of MMA very slowly. 1,1,1‐Trichloroalkanes, RCCl₃, are good initiators. For all the R groups tested, the number‐average molecular weight M_n increases with conversion and polydispersities are low (1.1 < M_w/M_n < 1.3). The initiator efficiency factor increases with electrophilicity of the initiating radical (0.7 < f < 1). CCl₄ is a multifunctional initiator and the final M_n values are lower than targeted. This is explained by the generation of new polymer chains occurring once the third active site is created per chain. ATRP of MA initiated by CCl₃CH₂CF₂Cl or CCl₃C₈H₁₇ results in polymers with M_n values predetermined by the Δ [M]/[Initiator]₀ ratio (f close to 1) and narrow molecular weight distributions (M_w/M_n < 1.3 at high conversion). The polymerization is much slower than that of MMA, but can be considerably accelerated by use of Cu(0) metal while maintaining an excellent control over molecular weights and polydispersities.     

Vinyl polymerization, 311. Synthesis and polymerization of 2-bromoethoxyphenoxyphosphoryl methacrylate

2-Bromoethoxyphenoxyphosphoryl methacrylate ( 5 ) was synthesized by the reaction of 2-bromoethyl phenylchlorophosphonate ( 3 ) with silver methacrylate and then polymerized by a radical initiator. The resulting polymer was soluble in DMF, but insoluble in other organic solvents. The hydrolysis of the polymer with sulfuric acid led to the corresponding poly(methacrylic acid) with a molecular weight of M_n=4,4·10⁵ (P_n=5,1·10³). 5 was copolymerized with acrylonitrile and the monomer reactivity ratio was determined: r₁ = 2,20, r₂=0,27.     

Effect of tert‐Butyl Chloride on the Isoprene Polymerization with Neodymium Isopropoxide/Diisobutylaluminum Hydride and Neodymium Isopropoxide/Methylaluminoxane Catalysts

The effect of tert‐butyl chloride (tBuCl) as a third catalyst component on the isoprene polymerization with neodymium isopropoxide (Nd(OiPr)₃)/diisobutylaluminum hydride (Al(iBu)₂H) and Nd(OiPr)₃/methylaluminoxane(MAO) catalysts was examined in heptane at a fixed [Al]/[Nd] ratio of 30 and reaction temperatures of 30 and 60 °C. The Nd(OiPr)₃/Al(iBu)₂H catalyst was inactive without tBuCl, i.e., at [Cl]/[Nd] = 0, while it showed the highest activity under the conditions of [Cl]/[Nd] = 3.0 and an addition order of {Al(iBu)₂H + tBuCl} + Nd(OiPr)₃ to yield polyisoprene with relatively low molecular weight (M _n ca. 5 × 10⁴), broad MWD (M _w/M _n ca. 5.4), and high cis‐1,4 content (ca. 96%) at 30 °C. On the other hand, the Nd(OiPr)₃/MAO catalyst was effective at [Cl]/[Nd] = 0, and the most active at [Cl]/[Nd] = 1.0–1.5 with an addition order of {Nd(OiPr)₃ + MAO} + tBuCl to afford polymer with high molecular weight (M _n ca. 8 × 10⁵), fairly narrow MWD (M _w/M _n ca. 1.6) and high cis‐1,4 content (ca. 94%) at 30 °C. Thus, the novel Nd(OiPr)₃/MAO/tBuCl system features high activity, high molecular weight, narrow MWD, and high cis‐1,4 stereospecificity, as compared with the conventional Nd(OiPr)₃/Al(iBu)₂H/tBuCl system.

Effect of the [Cl]/[Nd] mole ratio on the cis‐1,4 contents with Nd(OiPr)₃/Al(iBu)₂H/tBuCl catalyst. Curve a: at 30 °C, 180 min; curve b: at 60 °C, 90 min.     

Stereocomplex Crystallization Behavior and Physical Properties of Linear 1‐Arm, 2‐Arm,and Branched 4‐Arm Poly(L‐lactide)/Poly(D‐lactide) Blends: Effects of Chain Directional Change and Branching

For number‐average molecular weight (M _n) below 1 × 10⁴ g mol^?1, the comparison of cold crystallization temperature and spherulite growth rate and crystallinity of linear 1‐arm, 2‐arm, and branched 4‐arm poly(L ‐lactide)/poly(D ‐lactide) blends exhibits that the effects of chain directional change and branching significantly disturb stereocomplex crystallization. In contrast, the comparison of glass transition and melting temperatures of linear 1‐arm, 2‐arm, and branched 4‐arm poly(L ‐lactide)/poly(D ‐lactide) blends indicates that the effects of chain directional change and branching insignificantly alter and largely increase the segmental mobility of the blends, respectively, and the crystalline thickness of the blends is determined by M _n per one arm not by M _n and is not affected by the molecular architecture.