Siloxane Content Research Articles

Degradation of polydimethylsiloxane- block-polystyrene copolymer

Thermal decomposition of polydimethylsiloxane-(azobiscyanopentanoyl ester)s (PDMS-ACP) in the presence of styrene (St) monomer yielded polydimethylsiloxane-polystyrene block copolymers (PDMS- b-PSt). The thermal and thermo-oxidative degradation of these copolymers was investigated by thermogravimetry, and compared with that of unmodified polystyrene (PSt). The apparent activation energies E a in the degradation process for PSt and PDMS- b-PSt were determined by Ozawa's method. The values of E a, in thermal degradation for copolymers increased with increasing initial conversion, and were comparable with the values for PSt. The incorporation of PDMS segments in the block copolymers improved the thermo-oxidative stability of PSt. However, the degradation of PSt segments in the copolymers was not affected greatly by the siloxane content.

THERMAL DEGRADATION STUDY OF SILOXANE-DGEBA EPOXY COPOLYMERS

Siloxane-modified DGEBA epoxy (ESDG) copolymers were prepared from Epikote 1001 and siloxane oligomers. Thermal stability studied by TGA of these ESDG copolymers indicates that thermal degradation is being effected by either structure or content of the siloxane moiety in the copolymers. The study reveals that siloxane-modified epoxy copolymer with phenyl-enriched siloxane oligomer (ESDG-7430) provides higher thermal stability than dimethyl siloxane modified copolymer (ESDG-8430). Delaying thermal degradation by the siloxane segment of ESDG copolymers is observed and the increase in thermal stability of copolymer is also observed consistently, with the increase of the siloxane content. These results indicate that the cause of the delaying degradation may be due to the siloxane segment being stable at the epoxy degradation temperature and the heat irradiated on the copolymer being absorbed by the siloxane segment which may dissipate that portion of thermal energy efficiently through its flexible siloxane structure. The delaying degradation behaviour is also confirmed by a direct pyrolysis/mass spectrometry (DP/MS) study, by the observation of the formation and contents (TIC and SIC) of the thermal degradative volatiles (TDVs). Nonflammability of ESDG copolymers as indicated by the LOI values is increased consistently with the increase in siloxane content in the copolymers. IR analysis and SEM/EDX observations on the char residue are also carried out.

Ion conductive poly(ethylene oxide-dimethyl siloxane) copolymers

A series of poly(ethylene oxide-dimethyl siloxane) copolymers, — [SiMe2O(CH2CH2O)n]m — (n = 2, 3, 4, 5, 6.4, 8.7, 13.3), were synthesised by the reaction of polyethylene glycol with dimethyl dimethoxy/diethoxysilane. Corresponding ion-conductive polymers were prepared by complexing these copolymers with salts (sodium tetrafluoroborate or ammonium adipate). The highest conductivity of these systems at room temperature was 3 × 10−4 S cm−1 and 6 × 10−5 S cm−1, respectively. The glass transition temperature of these copolymers is reported and is seen to be dependent on the length of the ether units. The effects of siloxane content, salt concentration, and temperature on the conductivity are discussed. © 1996 John Wiley & Sons, Inc.

Ion conductive poly(ethylene oxide‐dimethyl siloxane) copolymers

A series of poly(ethylene oxide-dimethyl siloxane) copolymers, — [SiMe2O(CH2CH2O)n]m — (n = 2, 3, 4, 5, 6.4, 8.7, 13.3), were synthesised by the reaction of polyethylene glycol with dimethyl dimethoxy/diethoxysilane. Corresponding ion-conductive polymers were prepared by complexing these copolymers with salts (sodium tetrafluoroborate or ammonium adipate). The highest conductivity of these systems at room temperature was 3 × 10−4 S cm−1 and 6 × 10−5 S cm−1, respectively. The glass transition temperature of these copolymers is reported and is seen to be dependent on the length of the ether units. The effects of siloxane content, salt concentration, and temperature on the conductivity are discussed. © 1996 John Wiley & Sons, Inc.

Adhesive Properties of Siloxane Modified Polyimides and Application for Multi-Layer Printed Circuit Boards

Abstract The adhesive properties of various siloxane modified polyimides were studied for the development of suitable adhesive materials with good thermal stability. Their adhesive properties were influenced by siloxane content in the polymer backbone and the structure of the aromatic component. Among them, the copolyimides with small amounts of the siloxane unit showed the better lap shear strength compared with the corresponding all-aromatic polyimides. They had excellent adhesive strength to various substrates. Their adhesive durability under the highly humid condition (25°C, 90%RH) was also improved mainly due to their lower moisture sorption and lower moisture permeability. However, further siloxane modification lowered their adhesive strength and durability. On the other hand, thee T-peel strength of copolyimides was lowered according to the increase of siloxane content. Based on this study, a new type of adhesive film which was composed of a copolyimide as a major component, SPB-505A, was developed...

Synthesis and impact properties of siloxane-DGEBA epoxy copolymers

Siloxane-incorporated epoxy (ESDG) copolymers were prepared by a hot-melt method. IR, 1H- and 13C-NMR are used to determine the structures. The data on the molecular properties indicate that reaction proceeded with a random polycondensation without involving the opening of the oxirane ring in the epoxy structure. Lowering Tgs with increasing siloxane content in copolymers are observed except for the copolymer modified with PDMS siloxane oligomer. Thermal stability data indicate that siloxane moiety exerts its thermal stability on the copolymer through dissipation of the heat, thus delaying thermal degradation of copolymers. Increasing impact strengths in J/M in the range of 22.0–59.0 are observed for copolymers and the improvement of the impact strength is closely related to the structure and content of siloxane oligomers in copolymers. A rough surface was observed by SEM examination on the propagation surface of the copolymeric impact specimen, while a smooth surface is observed on the unmodified epoxy specimen. The EDX analysis reveals these protruded features are Si-rich segments. The morphological observations suggest the siloxane segment may act as a toughening agent in the epoxy networks, thus contributing to the impact improvement of the copolymers. © 1996 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 34:1907–1922, 1996

Preparation and structural determination of siloxane-modified sulfone-containing epoxy resins

Siloxane-modified sulfone-containing epoxy resins (ESBS) were prepared by polycondensation of PMPS and/or PDMS siloxane oligomers with EBS, the sulfone-containing epoxy resin. Structures were analyzed by IR, 1 H-, and 13 C-NMR. The siloxane content in the copolymers was determined by 1 H-NMR with an integration technique. Epoxy equivalent weight (EEW) determination indicated that the oxirane ring of EBS was intact with this hot-melt procedure. The GPC measurement of these ESBS copolymers showed that molecular weight (MW) increased with increasing siloxane content in PMPS-modified copolymers. Evidence of siloxane incorporation in the copolymer was discussed.

Preparation and structural determination of siloxane‐modified sulfone‐containing epoxy resins

Siloxane-modified sulfone-containing epoxy resins (ESBS) were prepared by polycondensation of PMPS and/or PDMS siloxane oligomers with EBS, the sulfone-containing epoxy resin. Structures were analyzed by IR, 1H-, and 13C-NMR. The siloxane content in the copolymers was determined by 1H-NMR with an integration technique. Epoxy equivalent weight (EEW) determination indicated that the oxirane ring of EBS was intact with this hot-melt procedure. The GPC measurement of these ESBS copolymers showed that molecular weight (MW) increased with increasing siloxane content in PMPS-modified copolymers. Evidence of siloxane incorporation in the copolymer was discussed. © 1996 John Wiley & Sons, Inc.

Surface behavior of dilute blends of poly(vinyl chloride) with siloxane–urethane–ethyleneoxide oligomers

AbstractX‐ray photoelectron spectroscopy is used to study the surface segregation of siloxane in blends of poly(vinyl chloride) with siloxane–urethane–ethyleneoxide oligomers. At high concentration of the oligomeric additive, the surface segregation of siloxane in the blends strongly depends on the molecular architecture of the additive: the segregation is much higher when the siloxane blocks are at the ends of the oligomeric chains. At low additive concentrations, the surface segregation of siloxane is governed solely by the siloxane concentration in the bulk. © 1995 John Wiley & Sons, Inc.

Synthesis and Characterization of Triphenylphosphine Oxide-Containing Poly(Aryl Imide)-Poly(Dimethyl Siloxane) Randomly Segmented Copolymers

Abstract Poly(aryl imide)-poly(dimethyl siloxane) randomly segmented copolymers were synthesized by essentially a one-step solution imidization process in a solvent system consisting of predominately o-dichlorobenzene with a small amount of n-methylpyrolidone. This solvent combination was selected because of its ability to afford homogeneous solutions throughout the polymerization process. This enabled copolymers of any desired poly(dimethyl siloxane) composition to be prepared. A hydrolytically stable triphenylphosphine oxide containing diamine, bis(3-amino-phenoxy-4′-phenyl)phenylphosphine oxide, was utilized as a chain extender and together with oxydiphthalic anhydride formed the hard segment in these copolymers. The soft segment was formed from α,ω-aminopropyl poly(dimethyl siloxane) oligomers of controlled molecular weight. The presence of phosphorus and silicon contributes several unique properties to the system, including enhanced solubility, thermal stability, and flame resistance. High molecular weight copolymers containing up to 60% (w/w) of the poly(dimethyl siloxane) segments were successfully prepared using this method. Gel permeation chromatography analysis, based on a universal calibration curve in CHCl3, was performed to determine the molecular weights and distribution. These copolymers with 40-60% (w/w) poly(dimethyl siloxane) exhibited upper Tg values ranging from 130 to 180°C and showed substantial char yields at 750°C in air, which increased with siloxane content. Dynamic mechanical analysis confirmed the anticipated microphase behavior by the presence of two separate glass-transition regions. Both small angle x-ray scattering and transmission electron microscopy measurements determined on well-characterized transparent cast films were used to better demonstrate the multiphase nature of these copolymers.

Surface enrichment of siloxanes with covalent bound ultraviolet (UV) absorber groups

The ability of siloxanes with UV absorber groups to enrich at the surface of cast polystyrene films was studied. Model compounds were siloxanes of the type Me3SiO(SiMe2O) n (SiMeRO) m SiMe3, withR representing a 2-hydroxy-benzophenone-4-oxypropyl group. Surface studies were carried out by contactangle measurements and ESCA (Electron Spectroscopy for Chemical Application) investigations. UV absorbers with a high content of dimethylsiloxane units strongly enrich at the surface of polystyrene, forming a thin surface layer with a high siloxane content. UV absorbers with few or no dimethylsiloxane units pe hydroxybenzophenone group are evenly distributed in the polymer matrix. ESCA sputter depth profiles are also given. Migration studies show that the siloxanes are delivered from the bulk to the surface subsequently after sputtering.

Synthesis and characterization of siloxane-modified epoxy resin

Epoxy resins of the EBS, a bis-p-phenol S modified diglycidyl ether of bis-p-phenol A and the ESBS, a siloxane modified EBS epoxy resin were prepared. Both structures of EBS and ESBS were elucidated with IR,1H NMR, and13C NMR. The near perpendicular comformation of two phenyl rings of sulfone has been introduced into the epoxy resins of EBS und ESBS for Me increase of Me Tg. Some curing and thermal characteristics of these modified EBS and ESBS epoxy resins were studied. The curing patterns of ESBS and ESBS indicated the similarity with that of the DGEBA epoxy resins. Tg measurements resulted an increasing order of We ESBS (Tg of 141 °C), EBS (Tg of 135 °C) and then followed by Epons 1004 (Tg of 104 °C), 1001 (Tg of 101 °C) and 828 (Tg of 100 °C) in samples tested under the same conditions. Thus the substantial improvement of the thermal stability of the modified epoxy resins was indicated. Compatibility characteristics of the EBS and ESBS as indicated by the SEM/EDS is that an ESBS up to 30 % of the siloxane content was found to be compatible but not miscible with the Epon, a phenolic epoxy resin of DGEBA.

Water Resistance of Poly(Imide-Siloxane) Adhesives: Diffusion Coefficients by Gravimetric Sorption

Abstract Diffusion coefficients of water vapor in a polyimide homopolymer and poly(imide-siloxane) multi-block copolymers of different siloxane concentration were determined from gravimetric sorption experiments. Diffusion coefficients were of the order of magnitude of 10−8 cm2/sec. Higher levels of siloxane incorporation caused a definite increase in the diffusion coefficient, indicating a decreased resistance to water ingression. The increase in diffusion was found to be influenced by siloxane block length and was interpreted in terms of free volume and morphology. The diffusion coefficient of the 10-weight-percent PDMS copolymer, however, was found to be the same within error as that of the polyimide. This and a previous surface study suggested that an increased surface water resistance may be achieved at low siloxane concentrations without greatly increasing the bulk diffusive properties to undesirable levels.

Water Resistance of Poly(imide-siloxane) Adhesives: An IGC Surface Energetics Study

Abstract Inverse Gas Chromatography was utilized to examine the interaction of water vapor with the surfaces of a polyimide homopolymer and poly(imide-siloxane) random-block copolymers of increasing siloxane content. The studies employed 45-60 meter, thin-polymer-film mega-bore capillary columns to maximize surface area. The free energies of specific surface interaction with water and the dispersive components of the solid surface free energies were determined. An increase in the polymer siloxane content from 0-wt% to 10-wt% resulted in a decrease of approximately 4 kJ/mol in the free energy of water-specific surface interaction. A further increase in siloxane content to 30-wt% was not found to increase surface water resistance significantly. Dispersive components of the solid surface free energies of the copolymers were comparable to values reported for poly(dimethylsiloxane) homopolymer.

Structure and gas permeability of siloxane-imide block copolymer membranes: 1. Effect of siloxane content

Abstract Siloxane-imide block copolymer membranes with various siloxane contents were prepared and their dynamic viscoelasticity, sorption of carbon dioxide, and permeability of carbon dioxide, oxygen and nitrogen were studied. The siloxane-imide block copolymer consists of a microphase separated structure of imide-rich and siloxane phases, and the mechanical properties of the siloxane-imide block copolymer are well retained up to a siloxane content of about 20 wt%. The amount of carbon dioxide sorbed into the siloxane-imide block copolymer decreases with the introduction of siloxane, reflecting the less-sorptive capability of the siloxane group. The sorption behaviour of the block copolymers is interpreted in terms of a dual-mode sorption theory, which is applied to glassy imide-rich phases. On the other hand, the permeability coefficients of carbon dioxide, oxygen and nitrogen are remarkably increased with siloxane content when the latter is more than 10 wt%, and the permselectivity of oxygen to nitrogen is decreased with siloxane content. These behaviours are interpreted by considering the arrangement of the two phases in the membrane.

Photosensitive polyimidesiloxanes

AbstractPhotosensitive polyamic acid involving substituted 3, 5‐diaminobenzamide has been developed for photopatternable polyimidesiloxanes. This precursor, formulated with photosensitizers, was used to develop fine patterns by i‐line UV exposure. The curing of polyamic acid was investigated by using FTIR and physical property measurement. The cured film has a high glass transition temperature depending on the siloxane content. It is stable up to 400°C and loses some of the substituted groups on heating to 500°C. The modulus, dielectric constant, and water absorption decreased with higher siloxane content.

Synthesis and properties of silethynylene-siloxane alternating copolymers

A series of novel silethynylene-siloxane alternating copolymers with variation of siloxane contents and substituents on the silicon atoms has been prepared. Reactions of bis(hydroxydiphenylsilyl)-ethyne with bis( N-methylacetamido)diphenylsilane or bis( N-ethylacetamido)dimethylsilane in THF gave polymers with molecular weights in the range of 5800 to 23,000. The polymers for which all substituents on the silicon atoms are phenyl groups have T ms at 155–174° and 10% weight loss temperatures at 503–521°.

Graft Copolymerization of Polydimethylsiloxane Macromonomers with Isopropenyl-1,3,5-triazines

Polydimethylsiloxane macromonomers (M1) having various molecular weights were copolymerized with two isopropenyltriazines (M2), 2-amino-4-anilino- and 4-(N-octadecylanilino)-6-isopropenyl-1,3,5-triazine (AAIT and N18), using azobisisobutyronitrile as an initiator in tetrahydrofuran. r1 decreased from 0.50 to 0.10 and r2 increased from 1.97 to 6.47 with the molecular weight of macromonomer for AAIT (M2). Glass transition temperature (Tg) of the graft copolymers consisting of AAIT segments slightly increased with the molecular weight of macromonomer. The second Tg of silicone segment was observed the below −100°C. The degree of lowering of Tg for the graft copolymers of N18 was larger than that of graft copolymers of AAIT with increasing the siloxane content.

An XPS study of the surface–bulk compositional differences in siloxane‐containing block copolymers and polymer blends

AbstractX‐ray photoelectron spectroscopy (XPS) is used to compare the surface behavior in various binary systems of poly(dimethylsiloxane) with poly(bisphenol A sulfone) and poly(bisphenol A carbonate). All the systems studied show a pronounced surface enrichment in siloxane. At a fixed siloxane concentration in the bulk the lowest extent of surface enrichment is observed in the +eat copolymers, next go the blends of copolymers in homopolymers, and the highest extent of surface enrichment is characteristic of the blends of homopolymers. The blends of two copolymers show an unexpected surface behavior: The addition of minor amounts of a siloxane‐rich copolymer to another copolymer possessing a much lower siloxane content decreases (rather than increases) the surface siloxane concentration of the latter. A microscopic model is suggested to explain the observed surface behavior. The model involves the formation of a “quasi‐two‐dimensional” overlayer of additive's macromolecules on the blend surface, with the macromolecules oriented preferentially parallel to the sample surface.

Synthesis and blend behavior of high performance homo- and segmented thermoplastic polyimides

New synthetic methodology was developed as part of an effort to increase the processibility of high Tg polyimide homo− and copolymers, suitable as matrix resins and structural adhesives. Molecular weight and end group control together with solution imidization techniques were successfully employed to convert a variety of poly(amic acid) intermediates to fully cyclized polyimides. The solution imidization was conducted in N-methylpyrrolidone (NMP) with o-dichlorobenzene used as the azeotroping agent at 165–190°C. This technique has produced products which are more soluble than polyimides prepared previously by bulk thermal cyclization of poly(amic acids) at temperature of 300°C. They are also more stable than “chemically” imidized materials. In addition, incorporation of the monofunctional reagent phthalic anhydride provides nonreactive phthalimide end groups and controlled molecular weight. This latter feature significantly further improved the melt and solution processibility of the resulting polyimides. In this study thermoplastic, fully cyclized polyimides of 10 000, 20 000, and 30 000 Mn were prepared which displayed glass transition temperatures ranging from 260–353°C, with the highest Tg observed with phthalimide capped polyimide systems derived from 6F-dianhydride and p-phenylene diamine. Tough, transparent films were prepared from polymers of 20 000 and 30 000 g/mol by casting from NMP solution or by compression molding at 50–70°C above the glass transition temperature. For purposes of molecular weight assessment, t-butyl phthalic anhydride was used as the end blocker. This permitted 400 M-Hertz proton NMR to be used for assessing the concentration of end groups. Comparison of the 18 aliphatic protons at the end of the chain allowed Mn values to be determined, which agreed well with theory. A series of poly(arylene ether ketone)/aromatic polyimide blends were investigated to determine the influence of structural variation and composition on miscibility. As an extension to the PEEKTM/UltemTM blend system, which has been reported to be miscible over all proportions, this study examined how structural variations in both the poly(arylene ether ether ketone) and the polyimide portions affect miscibility. In particular, replacement of the hydroquinone fraction in PEEKTM with bisphenol A or sulfonyl diphenol produced an amorphous polymer which was no longer miscible with UltemTM. Polyimide structures modified by employing 3,3′,4,4′-benzophenonetetracarboxylic dianhydride (BTDA) and 4,4′-[1,4-phenylene-bis-(1-methyl ethylidene)] bisaniline (Bis P) diamine to obtain higher glass transition temperatures were also investigated. This system afforded homogeneous blends with PEEKTM when the (Bis P) diamine was utilized in the synthesis of the polyimide. Furthermore, up to 50 mole percent of hexafluoro-bis-dianhydride (6FDA) could be substituted for BTDA without loss of miscibility. However, when the more polar 3,3′-diaminodiphenylsulfone diamine was employed, immiscible blends resulted. An additional important variant has been to incorporate polyimide siloxane segmented copolymers into the PEEKTM blend system. The polyimide segment can be designed to be miscible whereas the siloxane portion is homogeneously dispersed into a second phase which, in fact, enriches the surface behavior quite dramatically in siloxane content. The latter could be of some importance in allowing for atomic oxygen resistance and possibly improved flame resistance behavior.