Copolymer solutions methylene chloride

Solubility behavior of the copolymers in methylene chloride was examined by preparing a 103 solution in warm methylene chloride and allowing the solution to stand for two days at room temperature. The precipitate, if any, was filtered off under nitrogen pressure using a 0.45/t Millipore filter, washed with cold methylene chloride, and dried under vacuum. The soluble fraction was recovered by precipitation with methanol. A similar procedure was followed with m-xylene a 10% solution of the copolymer was heated overnight on a steam bath, the precipitate filtered off, dissolved in chloroform, and reprecipitated with methanol. 

In Fig. 49 the dependences of D, on copolymers composition are adduced, about which the following should be said. All values D, were determined for copolymers solution in chloroform, but copolymers synthesis was realized in other solvents APESF — in dimethylsulfonoxide and the two remaining copolymers — in methylene chloride. Since the interactions polymer-solvent fix the macromolecular coil stracture in synthesis process [46], then it is necessary either D, determination for the indicated solvents or recalculation of the value Dj. in chlo-... 

Silicone-PC block copolymers CgHi4, methylene chloride Casting from a homogeneous solution that favors the hard segments yielded hetter results than from mixed solvents from which PC blocks preferentially separated to form a discontinuous dispersion or network. Capillary viscometer, GPC, TMA, DMA (Maung et al. 1983)... 

Evidence for the block-type nature of the copolymers is provided by an analysis based on the ability of to form a complex with methylene chloride that is insoluble in methylene chloride. (11) When each of the coupled copolymers described above is dissolved in methylene chloride, a precipitate forms and can be isolated by filtration. Both 1 and the second polymer are present in the soluble fraction and both are present in the precipitate. Since 1 normally precipitates quantitatively from methylene chloride solution and the other polymers remain soluble, the coupled products must be block copolymers. 

The resulting styrene/maleic acid copolymer is soluble in hot water, in contrast to the starting material the aqueous solution of the product gives a distinctly acid reaction. The disappearance of the anhydride moiety can be verified by IR or C-NMR spectroscopic methods.The IR spectra of polymers should be recorded from a film of the sample prepared on a KBr pellet (freshly made from KBr powder). For this, a drop of a solution of the polymer in a low-boiling solvent (e.g.,THF, methylene chloride) is placed on the pellet.The residual solvent can often be removed directly in the IR beam.The resulting spectra are characterized by their sharp bands. 

About 20 g of a mixture of 4-vinylphenyldialkyl/arylsilane and styrene was introduced into an ampule of 25 ml capacity in the presence of AIBN (0.2 mole%). The polymerization procedure was the same as that used for homopolymerization. However, the conversion was limited to about 10% (about 4 h). The copolymer was isolated by precipitation of the methylene chloride solution into methanol and dried under vacuum at 40 °C for 6 h. 

The homopolymer of DMP dissolves readily in methylene chloride but precipitates on standing as a crystalline polymer-CH2Cl2 complex, providing a method for distinguishing between block copolymers and mixtures of homopolymers. Random copolymers prepared by methods a and b form stable solutions in methylene chloride. Copolymers with a 1 1 ratio of DMP and DPP prepared by methods c and d also yield stable methylene chloride solutions. Since the NMR spectrum shows that the DMP portion of these materials is present as a block and the solubility in methylene chloride shows that DMP homopolymer is absent, these copolymers have the block structure. They can be separated by crystallization from m-xylene into an insoluble DPP-rich fraction and a soluble DMP-rich fraction, both fractions having the NMR spectra characteristic of block copolymers. A typical 1 1 copolymer prepared by adding DMP to growing DPP polymer yielded 35% of insoluble material... 

Oxidation of a mixture of equivalent weights of the two low-molecular-weight homopolymers at 25°C with a diethylamine-cuprous bromide catalyst yielded a copolymer that formed stable solutions in methylene chloride and could not be caused to crystallize by stirring with a 3 1 methanol/toluene mixture, a procedure that results in crystallization of DMP homopolymer or of the DMP portion of DMP-DPP block copolymers. The NMR spectrum was identical with that of the polymer obtained by simultaneous oxidation of the two monomers. 

Twenty percent solutions in methylene chloride of the two copolymers prepared by Procedures 1 and 2 were stable indefinitely, showing that no significant amount of dimethylphenol homopolymer was present and that the DMP blocks must be in the form of a block copolymer. Separate experiments using blends of DMP homopolymers with random copolymers or with DPP homopolymer showed that DMP homopolymer, even of very low molecular weight (DP 15), could be detected easily if present to the extent of 5% of the total polymer. 

It was first intended to remove styrene homopolymer and unreacted cellulose (in the form of triacetate) by alternate extractions with benzene and a 1 1 methylene chloride-methanol mixture, but this was not successful. Therefore, a fractional precipitation method was adopted. The acetylated apparent graft copolymer was dissolved in a methylene chloride-methanol mixture (80 20 by volume). Methanol was very slowly added to the solution to precipitate the styrene homopolymer and the true graft copolymer. Dissolution in the methylene chloride-methanol mixture and precipitation with methanol were repeated four times. The final solution contained 45.0-46.3% methanol. 

The acetylated true graft copolymer was dissolved in methylene chloride, acetone was added to the solution to obtain a 1 1 methylene chloride-acetone composition of the solvent, concentrated hydrochloric acid was added to obtain a 3N solution, and hydrolysis was carried out for 72 hr at 60 °C. The hydrolysis proceeded not in a homogeneous but in a highly swollen state. The branch was precipitated by pouring the hydrolysis mixture into methanol. A part of the precipitated branch was dissolved in m-cresol and filtered. The other part was treated with 1 2 acetic anhydride-pyridine mixture for 15 hr at 100 °C to acetylate cellulose fragments at the end of polystyrene brandies. 

We recently have reported our initial studies on step-growth block copolymers containing segments of poly (aryl ethers) and poly (aryl carbonates) (9,10). The multiblock [ A-B ]n block copolymers were prepared by phosgenation in methylene chloride/pyridine solution either by what was termed an in situ or by a coupled oligomer technique (JO). The choice of polycarbonates and poly (aryl ethers) for initial studies was based on the several considerations. Copolymerization is feasible since the end groups in the two oligomers can be identical, as shown in Structures 1 and 2. Considerable information is available in the... 

Their hydrophobic/hydrophilic content seems to be just right for applications in cancer and gene therapies. Such nanospheres are prepared by dispersing the methylene chloride solution of the copolymer in water and allowing the solvent to evaporate [38]. By attaching biotin to the free hydroxy groups and complexa-tion with avidin, cell-specific delivery may be attained.NMR studies of such systems [39] revealed that the flexibility and mobility of the thus attached PEG chains is similar to that of the unattached PEG molecules dissolved in water. Re-... 

Stirred solutions of each polymer or copolymer at a concentration of 10 mg./ml. were Irradiated In air at 25°C In a quartz vessel with the light from a low-pressure mercury lamp at an absorbed Intensity of 2.95 x 10 quanta ml sec. . Polymer films, evaporated from DMM or methylene chloride solutions on quartz cuvettes or plates and vacutim dried, were Irradiated In air at about 35°C In a Rayonnet Model RPR-100 Photochemical Reactor containing 12 low-pressure mercury lamps the Incident radiation at the films was 1.3 x 10 quanta cm" sec"l. 

The synthesis of the corresponding poly(amic alkyl ester), on the other hand, involved the incremental addition of PMDA diethyl ester diacyl chloride in methylene chloride to a solution of the oligomer and 3FDA in NMP containing pyridine as the acid acceptor (Scheme 9). Alternatively, the diamino functional oligomers could be utilized in an analogous fashion to yield the graft copolymers (Scheme 10). In these experiments, the meta isomer of PMDA diethyl ester diacyl chloride was used primarily due to its enhanced solubility and lower soften-... 

Films were formed by the evaporation of methylene chloride solutions on one inside surface of a quartz fluorescence cell or on quartz plates. Irradiations were carried out in a Rayonet Photochemical Reactor fitted with low-pressure mercury lamps. The incident radiation intensity on the films was 10 6 Einstein cm 2 min+1. Absorbed intensity is based on energy absorbed by the styrene units of the polymers for the alternating copolymer this was 0.95 of the total energy absorbed at 254 nm. Film thicknesses were of the order of 25 / ni a thickness effect was not observed in the 10-40 / m range, but a small correction factor of 1 — T (254 nm), where T is transmittance, was applied where T was greater than zero. 

Torikai et al. [1994] compared the effects of gamma irradiation of films of PS/PMMA blends and PS-PMMA copolymer (co-PS-PMMA) (Table 11.9). Polymer films were cast from methylene chloride solutions and were dried under vacuum. Based on the UV and FTIR spectroscopy, and viscosity measurements, Torikai et al. [1994] concluded that whereas the presence of PS in the copolymer provided protection against radiation-induced degradation to the PMMA units, similar... 

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