Ryszard Szymanski

Molecular weight distribution in living polymerization proceeding with reshuffling of polymer segments due to chain transfer to polymer with chain scission, 1 : Determination of kp/ktr ratio from DPW /DPn data. Ideal reproduction of polymer chain activities

The molecular weight distribution (MWD) curves for polymerization systems with chain transfer to polymer leading to reshuffling of polymer segments (and broadening of the MWD), but not changing chain functionalities, were simulated by the Monte Carlo method. The bimodality observed in some distributions was explained by different distribution functions of chains which did not undergo reshuffling and of those which underwent the chain transfer reaction. Using this observation, a numerical integration method for computing DP w /DP n (and the MWD curves) in the systems under consideration was devised. Plots relating DP w /DP n to monomer conversion and k tr /k P are presented and a method of determination of k tr /k p from the DP w /DP n data is proposed.

Anionic Copolymerization of Elemental Sulfur with Propylene Sulfide. Equilibrium Sulfur Concentration

Abstract In the anionic copolymerization of elemental sulfur (S8) with propylene sulfide (P) below the floor temperature of elemental sulfur homopolymerization (Tf = 159°C), there is a certain concentration of elemental sulfur left when copolymerization is completed ([S8]eq). The dependence of [S8]eq on the feed ratio [P]0/[S8]0 and temperature was determined by using laser Raman spectroscopy, and this enabled us to distinguish between the S-S bonds in elemental sulfur and in the linear polysulfide. [S8]eq was found to decrease with increasing temperature and with an increasing [P0]/[S8]0 ratio. The experimental dependence of the average enthalpy and entropy of polymerization (δ[Hbar][Xbar], and δ [Sbar][Xbar]) on [Xbar], as described by the equilibrium …-CH2CH(CH3)SX − + S8 = …-CH2CH(CH3)SX+8 −, has shown that at [Xbar] ⇋; 9 the experimental δ[Hbar][Xbar] and δ [Sbar][Xbar] approach values determined earlier for the free radical homopolymerization of elemental sulfur …-Sn • + S8 ≤ …-S• n+8& The correspon...

New synthetic route to trialkyloxonium salts: alkylation of ethers with acyldialkyl cations

Acylium cations or complexes of acyl halides with nonmetal halides (e.g. PhCO+SbF6– or PhCOClSbCl5) react at low temperature with an excess of alkyl ethers (e.g. Me2O or Et2O) giving the corresponding trialkyloxonium salts.

The MPEG monophosphate ester: synthesis and characterization.

Methods of preparation of the phosphoric ester of monomethyl ether of poly(ethylene glycol) (MPEG-P) from MPEG (M n = 550 and 2000) and phosphoric acid (P), or its derivatives — pyrophosphoric acid (PY), polyphosphoric acid (PP) and POCl3– are described and compared. MPEG-P was isolated in a pure state (no detectable impurities) and characterized.

KINETICS OF ELEMENTARY REACTIONS IN CYCLIC ESTER POLYMERIZATION

Kinetics of the polymerization of L-lactide (LA) and e-caprolactone (CL) initiated with dialkylaluminum alkoxide, aluminum trialkoxide and related metal alkoxides is reviewed. The former give aggregating active species, and a method is described allowing simultaneous determination of the rate constants of propagation and aggregation equilibrium constants. It has been shown that tin“ dicarboxylate (dioctoate) requires a coinitiator in order to start polymerization. Both kinetic and spectroscopic evidence indicate that propagation proceeds on the —Sn-OR bonds. The major reaction accompanying propagation is the chain transfer-to polymer; either inter or intramolecular. Methods are described giving access to the rate constants of both transfers Finally, correlation is given between the atomic number of metal involved in the active species and the determined rate constants: the larger the atomic number, the higher is the rate constant of propagation and the less selective is the polymerization process.

Copolymers of 7‐oxabicyclo[2.2.1] heptane with 1,3‐dioxane and promesogenic telechelic oligomers thereof

Copolymers of 7-oxabicyclo[2.2.1 heptane (B) ( and of its 2-methyl derivatives) with 1,3-dioxane (D) were obtained by cationic copolymerization initiated with benzoylium hexafluoroantimonate. Structure of copolymers was determined by 1 H- and 13 C-NMR. The proportion of the acetal bonds in copolymers was additionally confirmed in studies of the products of hydrolysis (only the acetal bonds hydrolyze). D is unable to homopolymerize for the thermodynamic reasons and therefore mostly pseudoperiodic copolymers (-DB x -) y are formed. Nevertheless, the reshuffling reactions are responsible for the appearance of wrong units. These are: the separate oxymethylene and oxy-1,3-propylene units (P, subunits of D) located between two B units. Only the acetal bonds are cleaved in the acidic hydrolysis with dilute HCI. This gives the promesogenic telechelic oligomers of mostly HO-P-B x -OH structure. This article is the first to describe successful cationic copolymerization of cyclic acetal with a cyclic ether. Moreover, the inability of D to homopolymerize gives the thermodynamic basis of the pseudoperiodic copolymer formation.

Effect of the Configuration of a Bulky Aluminum Initiator on the Structure of Copolymers of l,l-Lactide with Symmetric Comonomer Trimethylene Carbonate

The effect of configuration of an asymmetric bulky initiator 2,2′-[1,1′-binaphtyl-2,2′-diyl- bis-(nitrylomethilidyne)]diphenoxy aluminum isopropoxide (Ini) on structure of copolymer of asymmetric monomer l,l-lactide (Lac) with symmetric comonomer trimethylene carbonate (Tmc) was studied using polarimetry, dilatometry, Size Exclusion Chromatography (SEC), and Carbon Nuclear Magnetic Resonance (13C NMR). When the S-enantiomer of Ini was used the distribution in copolymer chains at the beginning of polymerization is statistical, with alternacy tendency, changing next through a gradient region to homoblocks of Tmc. However, when R-Ini was used, the product formed was a gradient oligoblock one, with Tmc blocks prevailing at the beginning, changing to Lac blocks dominating at the end part of chains. Initiation of copolymerization with the mixture of both initiator enantiomers (S:R = 6:94) gave a multiblock copolymer of similar features but shorter blocks. Analysis of copolymerization progress required complex analysis of dilatometric data, assuming different molar volume contraction coefficients for units located in different triads. Comonomer reactivity ratios of studied copolymerizations were determined.

COPOLYMERIZATION OF TETRAHYDROFURAN WITH 1,3-DIOXANE AND TELECHELIC OLIGOMERS

Copolymers of tetrahydrofuran (T) with 1,3-dioxane (D) were prepared by cationic copolymerization initiated with benzoylium hexafluoroantimonate or triflic anhydride in order to prepare macromolecules having predominantly hydrolitically stable ether (interunit) bonds with some hydrolitically unstable acetal bonds. Structure of copolymers was determined by 1H and 13C NMR. The proportion of the acetal bonds in copolymers was additionally confirmed in studies of the products of hydrolysis (only the acetal bonds hydrolyze). D is unable to homopolymerize for the thermodynamic reasons and therefore, mostly copolymers with long blocks of T separated with one or a few units of D: (-D x T y-)z x<<y, are formed. Nevertheless, the reshuffling reactions are responsible for the appearance of “wrong” units. These are: the separate oxymethylene (M) and oxy-1,3-propylene units (P), subunits of D, located between two T units. Only the acetal bonds are cleaved in the acidic hydrolysis with dilute HCl. This gives telechelic oligomers of mostly HO-P-T x-OH structure.