Synthesis and thermal properties of diphenylsiloxane block copolymers (original) (raw)
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Poly(1,3-disila-1,3-diphenyl-2-oxaindane)-diphenylsiloxane-poly(dimethylsiloxane) block copolymers
Journal of Applied Polymer Science, 2006
The heterofunctional condensation of 1,3-dichloro-1,3-disila-1,3-diphenyl-2-oxaindane with dihydroxydiphenylsilane at various ratios of initial compounds in the presence of amines was carried out, and ␣,-dihydroxy(1,3disila-1,3-diphenyl-2-oxaindane)-diphenylsiloxane oligomers with various degrees of condensation were obtained. Corresponding block copolymers were obtained by heterofunctional polycondensation of synthesized ␣,-dihydroxy(1,3-disila-1,3diphenyl-2-oxaindane)-diphenylsiloxane oligomers with ␣,-dichlorodimethylsiloxanes in the presence of amines. Thermogravimetry, gel permeation chromatography, differential scanning calorimetry, and wide-angle X-ray analysis were carried out on the synthesized block coplymers. Differential scanning calorimetry and wide-angle X-ray studies of these copolymers showed that their properties were determined by the ratio of the lengths of the flexible linear poly(dimethylsiloxane) and rigid poly(1,3-disila-1,3-diphenyl-2-oxaindane)-diphenylsiloxane fragments in the main macromolecular chain. Two-phase systems were obtained with specific flexible and rigid fragment length values in synthesized block copolymers.
Polymer International, 2010
and poly(DMS-block-TMSHEMA) copolymers thus obtained were characterized using Fourier transform infrared and 1 H NMR spectroscopy and differential scanning calorimetry. After the deprotection of trimethylsilyl groups, poly(DMS-block-HEMA) and poly(DMS-block-EMA) copolymer film surfaces were analysed using scanning electron microscopy and X-ray photoelectron spectroscopy. The effects of the PDMS concentration in the copolymers on both air and glass sides of films were examined. The PDMS segments oriented and moved to the glass side in poly(DMS-block-EMA) copolymer film while orientation to the air side became evident with increasing DMS content in poly(DMS-block-HEMA) copolymer film. The block copolymerization technique described here is a versatile and economic method and is also applicable to a wide range of monomers. The copolymers obtained have phase-separated morphologies and the effects of DMS segments on copolymer film surfaces are different at the glass and air sides. Figure 4. 1 H NMR spectra of (a) PDMS, (b) PDMS-MAI, (c) poly(DMS-b-TMSHEMA) and (d) poly(DMS-b-HEMA).
Macromolecules, 2002
The structural features and the thermodynamics of melting of thermally reversible gels of poly(diphenylsiloxane) (PDPhS) formed from 1.5 to 85 wt % solutions in diphenyl ether (DPhE) have been studied by means of differential scanning calorimetry, X-ray diffraction, and electron scanning microscopy. It was established that gelation occurs as a consequence of the crystallization of PDPhS that leads to a specific spherulitic morphology; i.e., overlapped spherulite-like superstructures, which are composed of lamellar crystallites, form a three-dimensional skeleton filled with the solvent. The phase diagram of the PDPhS/DPhE system was constructed. Its particular feature, resulting from the crystalmesophase transition in the undiluted PDPhS, is interference between the crystal-isotropic solution and the thermotropic mesophase-isotropic solution equilibrium. The equilibrium temperature T m°and the heat ∆Hm°of a virtual crystal-isotropic melt transition in PDPhS in the absence of solvent were estimated (280°C and 10.34 kJ mol -1 ) through use of the Flory equation when taking the melting temperatures of the annealed gels as the equilibrium melting points of PDPhS crystals in the presence of DPhE. The isotropization temperature (∼560°C) of the mesophase, which cannot be measured experimentally because of PDPhS thermal degradation, was assessed by extrapolation of the mesophaseisotropic solution boundary curve on the phase diagram of the PDPhS/DPhE system to the 100% polymer concentration. Phase diagrams expected for the system solvent-crystalline flexible/semirigid-chain polymer, exhibiting a crystal-mesophase transition, were schematically considered and compared to that of the PDPhS/DPhE system. On the basis of this consideration, the conclusion was drawn that the mesophase behavior of PDPhS is connected, at least in part, with a relatively high stiffness of its macromolecules.
Apple Academic Press, 2020
Dehydrocondensation reactions of linear trimethylsiloxy group terminated methyl-hydro siloxane and methyl-hydro siloxane-dimethylsiloxane copolymers with α-hydroxyl-ω-trimethylsiloxydiphenylsiloxanes in the presence of dry potassium hydroxide have been studied and comb-type copolymers and block-copolymers (BCP) with various lengths of the side diphenylsiloxane fragments have been obtained. Depending on the lengths of the rigid and flexible initial oligomers microdomain structure of BCP were observed. The synthesized BCP were characterized by gel permeation chromatography, differential scanning calorimetric and X-ray methods.
Block-copolymers with Polyphenyl-α-Naphtylsilane Fragments in Dimethylsiloxane Chain
International Journal of Polymeric Materials and, 2001
The Wurtz-type reductive-coupling reaction of dichlorophenyl-a-naphtylsilanes was carried out both in the presence of metalic sodium in toluene solution and in a mixture of toluene and o-xylene (at I:I ratio) in the presence of sodium and catalytic amount of mercury. Oligomers of a. w-dichlorophenyl-a-naphtylsilanew ith various degrees of polymerization were obtained. By hydrolysis of a,w-dichlorophenyl-a-naphtylsilane the corresponding a,w-dihydroxydiorganosilanes has been obtained. The heterofunctional condensation of a,w-dichloro(dihydroxy)phenyI-a-naphtylsilanes with a,w-dihydroxy( dich1oro)dirnethylsiloxanes in the presence of acceptor pyridine has been carried out and polysilane-siloxane block-copolymers were obtained. Depending on the lengths of the rigid and flexible initial oligomers microdomain structure of block-copolymers were observed. The synthesized block-copolymers were characterized by gel permeation chromatography, differential scanning calorimetry and X-ray methods. Keywork Polysilane; Thermal-oxidative stability; Block-copolymers
Polymer, 1996
The influence of changing the block length of the polydimethylsiloxane block on the structure/property behaviour of two poly(ether ether ketone) polydimethylsiloxane (PEEK PSX) multiblock copolymers and their amorphous (non-crystallizable) ketamine precursors (PEEKt-PSX) was investigated. In the precursor block copolymer form, as well as the reduced amorphous and its corresponding semicrystalline form, a microphase morphology was noted from transmission electron microscopy (TEM) studies. For the solution cast precursor or the compression moulded reduced amorphous systems, the materials displayed two Tgs at ca.-130 and + 145°C, indicating strong phase separation. It was found that the room temperature tensile modulus of the PEEK-PSX multiblock copolymers with amorphous PEEK blocks of ~¢n = 4000 increased by 800% as the PSX block length was decreased from Mn = 5000 to Mn = 3000, i.e. the PSX mass fraction was decreased from 56 to 45%. This increase in stiffness resulted from developing a more continuous phase of the PEEK block component. After crystallization of the PEEK blocks, the room temperature modulus of both of the PEEK PSX copolymers increased by 200-500% incontrast totheir amorphous forms. Relative to the PEEK homopolymer of approximately the same molecular weight, the melt crystallization half-times for the multiblock copolymers were increased by a factor of 500 for the PEEK(4K)PSX(3K) system and by a factor of 1000 for the PEEK(4K)PSX(5K) system. A dramatic dependence of crystallization behaviour on thermal history prior to crystallization was observed in both microphase-separated block copolymer systems. Block copolymers thermally crystallized from the glassy state obtained a distinctly higher degree of crystallinity at a much faster rate of crystallization than the same copolymers crystallized from the melt at identical crystallization temperatures. Copolymers crystallized from the glass attained maximum levels of PEEK crystallinity of~ 40%, while those crystallized from the melt attained a maximum level of crystallinity of only 5-20%. The rate of crystallization for samples crystallized from the glass was ~ 30 times greater than that for samples crystallized from the melt at identical crystallization temperatures. Possible explanations for these observations are presented.
Journal of Polymer Science Part A: Polymer Chemistry, 2011
High molecular weight poly(dimethylsiloxane)/semicrystalline cycloaliphatic polyester segmented copolymers based on dimethyl-1,4-cyclohexane dicarboxylate were prepared and characterized. The copolymers were synthesized using a high trans content isomer that afforded semicrystalline morphologies. Aminopropyl-terminated poly(dimethylsiloxane) (PDMS) oligomers of controlled molecular weight were synthesized, end capped with excess diester to form a diester-terminated oligomer, and incorporated via melt transesterification step reaction copolymerization. The molecular weight of the polysiloxane and chemical composition of the copolymer were systematically varied. The polysiloxane segment was efficiently incorporated into the copolymers via an amide link and its structure was unaffected by low concentrations of titanate transesterification catalyst, as shown by control melt experiments. The homopolymer and copolymers were characterized by solution, thermal, mechanical, and surface techniques. The segmented copolymers were microphase separated as determined by differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and by transmission electron microscopy (TEM). It was demonstrated that relatively short poly(dimethylsiloxane) segment lengths and compositions were required to maintain single phase melt polymerization conditions. This was, in fact, the key to the successful preparation of these materials. The copolymers derived from short poly(dimethylsiloxane) segments demonstrated good mechanical properties, melt viscosities representative of single phase polymer melts, and were easily compression molded into films. ᭧ 1997