Anionic ring opening polymerization of 1-silacyclopent-3-ene

Summary 1-Silacyclopent-3-ene (I) undergoes anionic ring opening polymerization catalyzed by methyllithium/HMPA to yield poly(1-sila-cis-pent-3-ene) (II). II was characterized by ¹H, ¹³C, and ²⁹Si NMR, GPC, TGA and elemental analysis. The low molecular weight of II permits end group analysis. Pyrolysis of II gives high char yields. These have been characterized by EDS.     

Anionic ring opening polymerization of 1-phenyl-1-vinyl-1-silacyclopent-3-ene

Summary Poly(1-phenyl-1-vinyl-1-sila-cis-pent-3-ene) (I) has been prepared by the anionic ring opening polymerization of 1-phenyl-1-vinyl-1-silacyclopent-3-ene (II) co-catalyzed by n-butyllithium and hexamethylphosphoramide (HMPA) in THF at-78°C. I has been characterized by ¹H, ¹³C and ²⁹Si NMR as well as by IR and UV spectroscopy. The molecular weight distribution of I has been determined by gel permeation chromatography (GPC), its thermal stability by thermogravimetric analysis (TGA) and its glass transition temperature (T_g) by differential scanning calorimetry (DSC). Thermal degradation of I in an inert atmosphere gives a twenty-seven percent char yield.     

Hydrogenation of ring opening metathesis polymerization polymers

Various methods of hydrogenating ring opening metathesis polymerization (ROMP) polymers were investigated as part of an effort to improve their stability and increase their usefulness as matrix materials for nanocluster synthesis. Hydrogenation with Pd/BaSO₄ catalyst in high-pressure hydrogen gas was only partly successful and limited to unfunctionalized polymers such as polymethyltetracyclododecene. Block copolymers containing phosphine or carboxylic acid functionalities were successfully hydrogenated by diimide generated in situ from p toluenesulfonylhydrazide. © 1995 John Wiley & Sons, Inc.     

Anionic ring opening polymerization of 3,4-benzo-1,1-dimethyl-1-silacyclopentene

Summary Treatment of 3,4-benzo-1,1-dimethyl-1-silacyclopentene with a catalytic amount of n-butyllithium and HMPA in THF yields poly(3,4-benzo-1,1-dimethyl-1-silapentene). This polymer has the highest melting temperature, glass transition temperature and thermal stability of any poly (1-silapent-3-ene) yet prepared.     

Ring opening metathesis polymerization of dicyclopentadiene catalyzed by titanium tetrachloride adduct complexes with nitrogen‐containing ligands

Ring opening metathesis polymerization (ROMP) of dicyclopentadiene (DCPD) catalyzed by titanium tetrachloride adduct complexes such as TiCl₄ · 2L [L = pyridine (1), 2‐methylpyridine (2), 2,4,6‐trimethylpyridine (3), 3‐aminopyridine (4), 2‐hyroxypyridine (5)] and CH₃Li as cocatalyst was reported. The polymer was characterized by IR and ¹H‐NMR methods. Five influencing factors were also discussed. The catalyst systems TiCl₄ · 2L/CH₃Li (L = 2‐methylpyridine, 2,4,6‐trimethylpyridine) appeared to be very active for the ROMP of DCPD. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 3247–3251, 2000     

R-2-氨基-3-甲基-1,1-二苯基-1-丁醇的合成

R-2-氨基-3-甲基-1,1-二苯基-1-丁醇是一种合成手性催化剂的重要中间体。从原料R-缬氨酸经甲酯化,苄氧羰基保护制得R-2-苄羰基氨基-3-甲基-丁酸甲酯,然后与苯基溴化镁反应制得（R）-2-苄氧羰基氨基-3-甲基-1,1-二苯基-1-丁醇。接着在5%Pd/C催化加氢下脱除苄氧羰基得到目标化合物,总收率58%。此制备方法涉及的中间体及目标化合物易于纯化,总收率高且重现性好。     

Ring opening polymerization of lactide: kinetics and modeling

The ring opening polymerization (ROP) kinetics of L-lactide was studied in bulk at 150, 160, and 180?°C using stannous octoate [Sn(Oct)₂] catalyst and 1-pyrene butanol co-catalyst. The effect of different parameters namely, time and co-catalyst to catalyst ratio was studied on the properties of polylactide. The experimental results showed high conversion of L-lactide. The kinetics of L-lactide ROP follows the co-ordination insertion mechanism. The experimental results obtained were studied to account for the reversible activation, propagation, termination, and validated by modeling using MATLAB. The model developed successfully predicts the monomer conversion and the kinetics of L-lactide ROP.     

Ring opening polymerization initiated by methylaluminoxane/AlMe3 complexes

The ROP of cyclic ethers, carbonates and esters in the presence of commercially available methylaluminoxane/trimethylaluminum system has been studied. MALDI-ToF end groups analysis indicates that in a majority of systems considered, the polymerization process is initiated by insertion of a monomer into the Al-O-Al bond, generating alkoxide species, which are active sites in coordination polymerization. The polymerization of six-membered carbonates proceeds selectively, forming linear polydiols with high yields at moderate temperatures. The polymerization of oxiranes and lactones is, however, accompanied by back-biting reactions leading to cyclic oligomers. The interaction of oxirane with aluminoxane electrophilic sites causes also the formation of cationic species, which initiate the polymerization of THF. The cationic species formed in those systems were trapped by triphenylphosphine and identified by ³¹P NMR spectra.     

Polydispersity control in ring opening metathesis polymerization of amphiphilic norbornene diblock copolymers

Ring opening metathesis polymerization (ROMP) with Grubbs's catalyst was used to synthesize narrow polydispersity (PDI)diblock copolymers of norbornene (NOR) and norbornenedicarboxylic acid (NORCOOH). Norbornene (NOR) and 5-norbornene-2,3,-dicarboxylic acid bis trimethylsilyl ester (NORCOOTMS) were used as precursor monomers for thepolymerization. [NORCOOTMS]_m/[NOR]_n was converted to [NORCOOH]_m/[NOR]_n by precipitating the polymer solution in a mixture of methanol, acetic acid, and water. The conversion to 5-norbornene-2,3-dicarboxylic acid was evidenced by ¹H NMR. By polymerizing the bulkier NORCOOTMS precursor monomer first, lower PDIs were observed for the completed [NORCOOH]_m/[NOR]_n block copolymers in comparison to copolymers where the NOR block was polymerized first. The PDI of the diblock copolymers of [NORCOOH]_m/[NOR]_n decreased with increase in block length ofthe precursor NORCOOTMS monomer. This study shows that the PDI can be controlled by selecting a monomer with appropriate functionality as the starting block of the block copolymer to control the rate of propagation, R_p, as an alternative of using additives to change the reactivity of the catalyst.     

Metathesis ring opening polymerization of 5,6-dimethylenebicyclo[2.2.1]hept-2-ene

5,6-Dimethylenebicyclo[2.2.1]hept-2-ene ( I ) polymerizes in the presence of the two-component ring opening metathesis polymerization (ROMP) initiators WCl₆/(CH₃)4Sn and MoCl₅/(CH₃)4Sn. The product polymers were insoluble in all of many solvents investigated and are presumably cross-linked. The product polymers were investigated by IR and solid state ¹³C NMR spectroscopy, which established that the material consisted predominantly of poly(1,4-(2,3-dimethylene-cyclopentylene)vinylene) ( II ). A possible alternative route to II via thermal dehydrochlorination of poly(1,4-(2,3-bis(chloromethyl)cyclopentylene) vinylene) ( IV ) was also examined.     

Ring opening polymerization of 2,5-dihydro-2,5-dimethoxyfuran by electrochemical initiation

Summary 2,5-Dihydro-2,5-dimethoxyfuran (DHMF) was polymerized via constant current electrolysis (CCE), in CH₃CN-NaClO₄ solvent-electrolyte couple. Poly(DHMF) was obtained from the anolyte. The effect of current density, temperature, monomer and electrolyte concentrations on the polymer yield have been examined. The apparent activation energy for CCE of DHMF was found to be 37.2 kj/mol. The FTIR and ¹H-NMR analyses show that DHMF polymerizes by a ring opening. Molecular weight of poly(DHMF) was found by using cryoscopy.     

Well-defined phosphonated homo- and copolymers via direct ring opening metathesis polymerization

Phosphonated polymers with a well-defined molecular weight, composition and architecture have been prepared via ring opening metathesis polymerization (ROMP) of phosphonated and non-phosphonated norbornene imides at room temperature for the first time. ROMP was proven to be living and versatile. This enabled preparation of a broad range of phosphonated homopolymers, statistical copolymers, AB diblock as well as ABA and BAB triblock copolymers based on poly(norbornene imide)s with low polydispersity (1.09–1.32). Complete hydrolysis of phosphonated poly(norbornene imide)s under mild conditions yielded the phosphonic acid derivatives. Thermogravimetric analysis indicated high thermal and thermo-oxidative stability of the polymers. Free standing and transparent films with good mechanical stability were obtained from the phosphonic acid functional homopolymers, diblock and triblock copolymers. Combining these basic properties with the advantages mentioned above makes ROMP a promising pathway for accessing a wide diversity of phosphonated macromolecular structures. These new phosphonated polymers will open new perspectives in advanced application areas, which require a high level of control over polymer structure.     

Ring opening polymerization of 2-aminothiazole with iron(III) chloride

Poly(2-aminothiazole), PAT, was synthesized by the chemical polymerization of 2-aminothiazole, AT, with FeCl₃·6H₂O in 1,4-dioxane. The effect of temperature, monomer, and initiator concentration and polymerization time on the rate of polymerization was studied. The structural analysis of the polymer was carried out by elemental analysis and ¹H-NMR, FTIR, and UV–VIS spectroscopies. Thermal properties were studied by DSC and TGA. Conductivity measurements were carried out by four-probe technique and the number average molecular weight, M _n, of the polymer was determined by cryoscopy.     

Acyclic metathesis during ring-opening metathesis polymerization of cyclopentene

‘Living’ ring-opening metathesis polymerization (ROMP) permits the synthesis of narrow-distribution homopolymers and well-defined block copolymers - provided no side reactions occur. However, acyclic metathesis between the chain end and double bonds in the polymer backbone competes with propagation during ROMP of cyclopentene, even with a mild Mo catalyst, though the rate constant is some 1600-fold smaller. ‘Dead’ chains in the reaction mixture can also be attacked; the products of acyclic metathesis are tagged by quenching the ROMP reaction with pyrenecarboxaldehyde. The extent of acyclic metathesis can be minimized through proper choice of reaction conditions, permitting the synthesis of narrow-distribution polycyclopentene with 100 kg/mol molecular weight.     

Ring-opening polymerization of 1 -ethylbicyclo[2.2.1] hept-2-ene

1-Ethylbicyclo[2.2.1]hept-2-ene has been polymerized using a range of metathesis catalysts and the structure of the polymers determined by ¹³C n.m.r. spectroscopy. For a given catalyst the cis double bond content was lower and the head-tail bias greater than for polymers of the 1-methyl analogue. This is interpreted in terms of enhanced steric and polar effects brought about by the ethyl substituent.     

Stress-strain behavior and dynamic mechanical properties of poly(1,1-dimethyl-1-sila-cis-pent-3-ene), poly(1-methyl-1-phenyl-1-sila-cis-pent-3-ene) and of these polymers after crosslinking with sulfur

Mechanical properties of polymers can be described by their stress/strain curves and by their behavior under dynamic mechanical thermal analysis (DMTA). The purpose of this paper is to report such mechanical properties for two unsaturated polycarbosilanes: poly(1, 1-dimethyl-1-sila-cis-pent-3-ene) (I) and poly(1-methyl-1-phenyl-1-sila-cis-pent-3-ene) (II). Tensile strength, elongation at break, modulus, bending modulus, T_g, and tan δ for I, II and for sulfur crosslinked I and II have been measured. The influence of polymer molecular weight, quantity of crosslinking agent, cure time, presence of carbon black filler, the effect of crosshead speed, and frequency on these properties was investigated.     

Birch reduction of the dichlorocarbene adduct of poly(1,1-dimethyl-1-sila-cis-pent-3-ene)(Cl2C-I): synthesis and characterization of poly(1,1-dimethyl-3,4-methylene-1-sila-cis-pent-3-ene) CH2-I)

Summary Birch reduction of the dichlorocarbene adduct of poly(1,1-dimethyl-1-sila-cis-pent-3-ene) (Cl₂C-I) yields poly(1,1-dimethyl-3,4-methylene-1-sila-cis-pent-3-ene) (CH₂-I) which has been characterized by ¹H, ¹³C and ²⁹Si NMR spectroscopy as well as by elemental analysis. The molecular weight distribution of CH₂-I has been determined by GPC and its thermal stability by TGA. Its glass transition temperature was obtained by DSC.