High Molecular Weight Homopolymers Research Articles

Segregation of block copolymer micelles to surfaces and interfaces

The distribution of a diblock copolymer within a high molecular weight homopolymer matrix phase was determined quantitatively by forward recoil spectrometry. Cross-sectional TEM showed that excess copolymer segregation to the homopolymer/homopolymer and homopolymer/vacuum interfaces was due the preferential segregation of block copolymer micelles to these interfaces. It is argued that the segregation of block copolymer micelles is a manifestation of attractive interactions between polymer brushes, and between polymer brushes and a free surface, which are important in high molecular weight homopolymer matrices

Polymerization and copolymerization using high intensity ultrasound

AbstractAbstract: High intensity ultrasound has been used to prepare homopolymers and copolymers of styrene, methyl methacrylate and n‐butyl methacrylate. High molecular weight homopolymers are formed rapidly during sonication and are then subjected to a degradation process. The copolymers prepared by this method have similar structure and properties to those prepared using AIBN as an initiator.

Coordination polymerization of ω‐alkenoates and ω‐epoxyalkanoates

AbstractAs functional polymers have become more and more used, the need for a general synthesis of addition polymers with functional groups became greatly important. We have achieved the polymerization of ω‐alkenoates with coordination initiators of the Ziegler‐Natta initiation type using titanium trichloride‐based transition metal initiators modified with dialkylaluminum chloride. To accomplish this polymerization required that the ω‐alkenoates be precomplexed with dialkylaluminum chloride. High molecular weight homopolymers and copolymers with olefins have been obtained. The polymerization of ω‐epoxyalkanoates with coordinative anionic polymerization systems based on triethylaluminum/water/acetylacetone (1.0/0.5/1.0) has also been accomplished. Homo‐ and copolymers of high molecular weight and of relatively narrow molecular weight distribution have been prepared. All polymers and copolymers of functional olefins and epoxides have been characterized and the study of the reactivity of the functional groups attached via a flexible spacer to the polymer main chain has been started. Special attention was given to the classical cationic copolymerization of trioxane with derivatives of ω‐epoxyundecanoate to prepare novel functional polyoxymethylenes of potential commercial interest.

Synthesis, kinetic observations and characteristics of polyarylene ether sulphones prepared via a potassium carbonate DMAC process

The classical route for the synthesis of this family of macromolecules is via nucleophilic aromatic substitution of 4,4′-dichlorodiphenyl sulphone with bisphenates using dimethylsulphoxide (DMSO) and aqueous sodium hydroxide. High molecular weight homopolymers can be synthesized in a relatively short time. However, hydrolytic side reactions can limit its scope for the synthesis of both homopolymers derived from insoluble bisphenates and for copolymers. An alternate route is discussed herein that uses potassium carbonate/dimethylacetamide as base and aprotic dipolar solvent, respectively, for the synthesis of several homopolymers and copolymers derived from various bisphenols. In this system, excess potassium carbonate, unlike aqueous caustic, does not prevent the synthesis of high molecular weight macromolecules. Investigations of the kinetics and mechanism of this process were conducted. These studies demonstrated that this route deviates from the relatively simple second order kinetics previously observed for the aqueous sodium hydroxide/DMSO system. This deviation has been rationalized as resulting from the partially heterogeneous nature of the potassium carbonate.

Poly(ethyleneoxide-b-styrene) copolymers as solid—liquid phase transfer catalysts

Di- and tri-block copolymers of ethylene oxide and styrene function as effective phase transfer catalysts in the reaction of solid potassium phenoxide with n-butylbromide in refluxing toluene to give virtually quantitative yields of n-butyl phenyl ether. A wide range of copolymer structures have been examined and the catalytic activity is found to increase with M ̄ n of both the styrene and the ethylene oxide segments levelling off at M ̄ n styrene block ∼30 000 and M ̄ n ethylene oxide block ∼60 000. Beyond M ̄ n ethylene oxide block ∼100 000 rates of reaction drop again towards the value for a high molecular weight homopolymer of ethylene oxide. Kinetic analysis suggests the rate controlling process to be the bimolecular reaction between complexed potassium phenoxide and n-butyl bromide, and the activation energy for the reaction is the same as that for reactions catalysed by low molecular weight oligoethers. From the kinetic dependence of the concentration of copolymer catalysts, the dependence on the structure of individual copolymers and from the known physical behaviour of these copolymers in toluene solution, catalysis appears to involve micellar aggregates of copolymer chains.

Sulfur-Containing Vinyl Monomers. XVIII. Preparation and Polymerization of Vinyl Mercapto-4-methylthiazole and Properties of Its Polymers

Abstract Vinyl mercapto-4-methylthiazole (VMMT) was prepared by the reaction of sodium 2-mercapto-4-methylthiazole with 1,2-dichloroethane, followed by dehydrochlorination. This monomer was easily polymerized in the presence of light or radical initiator to give a relatively high molecular weight homopolymer (15,000-55,000). The radical copolymerizations with various monomers (M1) were also performed readily, and the following copolymerization parameters were obtained: r1 = 2.39, r2 = 0.338, Q2 = 0.605, e2 = −1.26 for VMMT (M1)-styrene (M2) at 60°C. The resulting homo-and copolymers were photodegrad-able. The reactivity of radical polymerization, and the thermal-and photodegradation behavior of the polymer were also discussed.

Sulfur-Containing Vinyl Monomers. XIV. Radical Polymerizations and Copolymerizations of Vinyl Mercaptobenzazoles

Abstract Vinyl mercaptobenzazoles [thiazole (VMBT), oxazole (VMBO), and imidazole (VMBI)] were prepared through dehydrochlorination of the respective β-chloroethyl mercaptobenzazoles. These monomers were found to undergo vinyl polymerization in the presence of light or radical initiator, α,α'-azobisisobutyonitrile, to give relatively high molecular weight homopolymers. From the results of radical copolymerizations of these monomers with various monomers, the copolymerization parameters were determined as follows: VMBT(M2): r1 styrene(M1): r1 = 2.12 ± 0.09, r2 = 0.336 ± 0.028, Q2 = 0.75, ez = −1.38; VMBO(M2)-styrene(M1): r1 = 2.61 ± 0.13, r2 = 0.274 ± 0.03, Q2 = 0.61, e2 = −1.38; VBMI(M2)-styrene(M1) r1 =4.0, r2 = 0.2, Q2 = 0.37, e2 = −1.17. The polymerization reactivities of these monomers obtained from these parameters were compared with those of other vinyl sulfide monomers and discussed.

ESR studies of polymer transitions. IV. Spin‐probe studies of styrene block copolymers

AbstractESR spin‐probe values of glass temperatures are reported for a series of di‐, tri‐, and radial block copolymers. With one exception, in which the hard phase is poly(t‐butylstyrene), the hard component is polystyrene (PS); the soft components include polybutadiene (PBD), polyisoprene (PI), hydrogenated PBD, hydrogenated PI, and poly(dimethyl siloxane) (PDMS). Tg's of the soft phase are in general agreement with those of the respective high molecular weight homopolymers; Tg's of the hard phase generally deviate widely from those of corresponding high molecular weight homopolymers. This deviation is interpreted in teens of a number of factors, including, the molecular weight of the hard phase, differences in solubility parameters for the two phases, percent of the hard phase present, and the presence of crystallinity. Comparison of Tg's determined by ESR with Tg's from dynamic mechanical methods on S‐B‐S triblocks of similar composition demonstrates that the ESR method is measuring the Tg of the interpliase and hence, in principle, its composition.

Rheological properties of poly(2,6‐dimethylphenylene oxide)—polystyrene blends

AbstractThe viscoelastic (VE) response of freeze‐dried blends of polystyrene (PS) and poly‐(2,6‐dimethyl phenylene oxide) (PPO) has been studied as a function of composition, frequency, and temperature to examine the degree of rheological compatibility. When blended together, the relaxation processes of both molecular species exhibit the same temperature dependence. However, the temperature dependence of the VE response is a function of composition. It is shown that this behavior can be predicted from the measured glass transition temperatures by assuming the additivity of the free volumes of the components. The properties of the blends are compared at equal free volumes. The effective segmental friction factor is found to be independent of composition while the modulus of the rubbery plateau increases with PPO concentration. This result is interpreted as a change in the entanglement molecular weight Me of the blends. When the changes in Me are considered, the relationship between the zero‐shear viscosity η0 and the 3.4 power of the weight‐average molecular weight, commonly found for high molecular weight homopolymers, predicts the compositional dependence of η0 for the PPO–PS blends. It is concluded that the PPO–PS system forms a rheologically compatible blend.

Synthesis and polymerization of O6-methylguanosine 5′-diphosphate

O 6-Methylguanosine 5′-diphosphate has been prepared from 6-chloro-2-aminopurine riboside by a three-step synthetic process. Conversion of the chloro compound to O 6-methylguanosine using sodium methoxide was followed by enzymatic phosphorylation of the riboside to form the 5′-monophosphate. The diphosphate was synthesized from the monophosphate through an imidazolidate intermediate. O 6-Methylguanosine 5′-diphosphate proved to be a good substrate for polynucleotide phosphorylase, yielding a high molecular weight homopolymer with an s 20 value of 9 at pH 11.

1:1 alternating copolymers of 1‐bicyclobutanecarbonitrile with styrene

AbstractHigh molecular weight, 1:1 alternating copolymers of 1‐bicyclobutanecarbonitrile with styrene were prepared in tetramethylenesulfone solution by complexing the electron‐poor bicyclobutane monomer with zinc chloride. Methyl 1‐bicyclobutanecarboxylate under these conditions gave copolymers containing a slight excess of styrene units (ratio 1:1.3 to 1:1.8). High molecular weight homopolymers of 1‐bicyclobutanecarbonitrile and of methyl 1‐bicyclobutanecarboxylate were prepared similarly. The tendency of the bicyclobutane nitrile to form 1:1 alternating copolymers is as great as that of its vinyl analog, acrylonitrile, and the synthesis of other alternating copolymers from this monomer should be possible.

Synthesis of poly-O-tert-butyl-L-serine and poly-L-serine.

AbstractThe synthesis of polymers containing O‐tert‐butyl‐L‐serine, O‐tert‐butyl‐DL‐serine, L‐serine, and DL‐serine is reported. The N‐benzyloxycarbonyl‐(L or DL)‐serine benzyl ester was used to synthesize the corresponding N‐benzyloxycarbonyl‐O‐tert‐butyl‐(Lor DL)‐serine benzyl ester. Catalytic hydrogenation of this material gave O‐tert‐butyl‐(Lor DL)‐serine. The reaction of O‐tert‐butyl‐(Lor DL)‐serine with phosgene produced the corresponding N‐carboxyanhydrides. The kinetics of polymerization of N‐carboxyanhydrides were investigated to facilitate, the preparation of block copolymers. The O‐tert‐butyl blocking group was removed from polymers by treatment with HCl and HBr in benzene. Both high molecular weight (water‐insoluble) and low molecular weight (water‐soluble) homopolymers have been prepared, as well as water‐soluble block copolymers of the type (DL‐serine)x (L‐serine)y, (DL‐serine)z.

The crystallization of high molecular weight poly‐(tetramethylene oxide) and related polymers

AbstractUsing dilatometric techniques, detailed investigations have been made of the crystallization and melting behavior of high molecular weight poly(tetramethylene oxide), low molecular weight poly(tetramethylene oxide) glycol, and a high molecular weight copolymer prepared by the chain extension of the glycol. The degree of crys‐tallinity is expressed as a function of time and temperature. Using fast melting rates, the apparent melting point of the bulk polymers has been found to depend on both the temperature of crystallization and the level of crystallization allowed to develop before melting. Extrapolation gave an estimated equilibrium melting point for high molecular weight homopolymer of about 51°C. The highest experimentally observed melting point was 43°C. Visual observations have been made on crystallization of these materials from dilute solution (⪕3%) in toluene. Under some experimental conditions crystallization was accompanied by gel formation while under other conditions two distinct and separable phases were formed. Measurements were made on the dissolution temperatures of solutions crystallized under different experimental conditions.

Polymers of fluorocarbon ethers and sulfides. I. Trifluoromethyl trifluorovinyl ether and sulfide

AbstractTrifluoromethyl trifluorovinyl ether (I) and sulfide (II) were prepared by dehalogenation of the corresponding 1,2‐dichlorotrifluoroethyl compounds. These were prepared from the reactions of trifluoromethyl hypofluorite with 1,2‐dichlorodifluoroethylene and trifluoromethane sulfenyl chloride with chlorotrifluoroethylene, respectively. The polymerization behavior of these, along with the known trifluoroethyl trifluorovinyl ether (III) was examined. Only III gave a high molecular weight homopolymer, and, along with I, copolymers. II was quite unreactive in all polymerization reactions. High molecular weight copolymers of I and III were obtained with tetrafluoroethylene, vinylidene fluoride, vinylene fluoride, ethylene, and chlorotrifluoroethylene. Those with vinylidene fluoride and ethylene were elastomers in both cases as was the copolymer of III with tetrafluoroethylene, I and II were reacted with CF3NO slowly to give low polymers and volatile products, the corresponding 1,3‐disubstituted oxazetidines. III was reacted with nitrosyl chloride to give a nitroso compound.