Structure investigation of organosilicon polymers by silicon-29 NMR

Engelhardt, G.; Jancke, H.

doi:10.1007/bf00255295

Cited by 78 publications

(29 citation statements)

References 4 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In 29 Si-NMR, one can readily distinguish Me 3 SiO-(M), O-SiMe 2 O-(D), MeSiO 3/2 (T) and SiO 2 (Q) species. In terms of applications to silicones, a variety of homopolymers, block copolymers, random and alternating copolymers, cocyclics etc have been analyzed by 29 Si-NMR [85][86][87][88]. Pellenbarg reports quantitative and qualitative analysis of silicones in sediment like matrices using 29 Si-NMR [89].…”

Section: Spectroscopic Methodsmentioning

confidence: 99%

A Primer on the Analytical Aspects of Silicones at Trace Levels-Challenges and Artifacts – A Review

2006

View full text Add to dashboard Cite

Silicones (polydimethylsiloxanes) find use in a wide variety of industrial and consumer product applications because of their outstanding properties. Potential human exposure to silicones occurs in the work place during manufacturing and product formulation, as well as through the normal use of consumer products containing them.The entry of silicones into various environmental compartments raised health and safety concerns from potential exposure and mandated numerous environmental and toxicological studies. Such studies require qualitative and quantitative determination of silicone species at trace levels. However, the ubiquitous presence of silicones coupled with their unique chemistry renders their analysis at trace levels challenging.This paper provides a consolidated account of various aspects of silicones that must be borne in mind to obtain reliable data. The following topics are discussed: differences in the chemistry of silicones vs carbon; precautions in sample handling to avoid losses and inadvertent chemical transformation; potential sources for artifacts and interferences that could lead to systematic errors and data misinterpretation; sources for background and the need for matrix matched blank experiments; distinguishing silicones from silicates to avoid overestimation; potential for incorrect structural assignments; preventing inadvertent contamination; and questionable claims on the presence of silicones in biological matrices including that of silicone implants.

show abstract

Section: Spectroscopic Methodsmentioning

confidence: 99%

A Primer on the Analytical Aspects of Silicones at Trace Levels-Challenges and Artifacts – A Review

2006

View full text Add to dashboard Cite

show abstract

“…Cross-polarization (CP) and direct polarization (DP) excitation methods in concert with magic spinning (MAS) allows one to obtain qualitative and quantitative information on composition, surface and bulk properties, local molecular environment of diverse silicon containing materials such as silica gels [12, 15], organosilicon polymers and resins [9, 16], mesoporous materials [17, 18], hybrid inorganic–organic materials [4, 5]. …”

Section: Introductionmentioning

confidence: 99%

A Solid-State NMR Investigation of MQ Silicone Copolymers

et al. 2013

View full text Add to dashboard Cite

The structure of MQ copolymers of the general chemical formula [(CH3)3SiO0.5]m [SiO2]n was characterized by means of solid-state magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy. The MQ copolymers are highly branched polycyclic compounds (densely cross-linked nanosized networks). MQ copolymers were prepared by hydrolytic polycondensation in active medium. 29Si NMR spectra were obtained by single pulse excitation (or direct polarization, DP) and cross-polarization (CP) 29Si{1H} techniques in concert with MAS. It was shown that material consist of monofunctional M (≡SiO Si (CH3)3) and two types of tetrafunctional Q units: Q4 ((≡SiO)4Si) and Q3 ((≡SiO)3SiOH). Spin–lattice relaxation times T1 measurements of 29Si nuclei and analysis of 29Si{1H} variable contact time signal intensities allowed us to obtain quantitative data on the relative content of different sites in copolymers. These investigations indicate that MQ copolymers represent dense structure with core and shell.

show abstract

“…Figure 1 shows a 29 Si NMR spectrum of the commercial phenyl group-containing copolymer (MW 336,000); peaks ranging from δ −26.35 to −35.86 ppm and from δ −40.75 to −48.94 ppm are assigned to the methyl phenyl siloxane unit (SiMePh) and di-phenyl siloxane unit (SiPh 2 ), respectively. [35] The ratios of SiMePh and SiPh 2 in the copolymer are calculated at 57.7 and 42.3 mol%, respectively according to NMR analysis. Figure 2 shows a series of 29 Si NMR spectra of the re-equilibrated polymers with different RI (containing a different ratio of phenyl groups), in comparison with the starting material.…”

Section: Resultsmentioning

confidence: 99%

High refractive index polysiloxane as Injectable, in situ curable accommodating intraocular lens

Hao

Jeffery

et al. 2012

Biomaterials

View full text Add to dashboard Cite

Functionalised siloxane macromonomers, with properties designed for application as an injectable, in situ curable accommodating intraocular lens (A-IOL), were prepared via reequilibration of a phenyl group-containing polysiloxane of very high molecular weight with octamethylcyclotetrasiloxane (D4) and 2,4,6,8-tetra(n-propyl-3-methacrylate)-2,4,6,8-tetramethylcyclotetrasiloxane (D4AM) in toluene using trifluoromethanesulfonic acid as a catalyst. Hexaethyldisiloxane was used as an end group to control the molecular weight of the polymer. The generated polymers had a consistency suitable for injection into the empty lens capsule. The polymers contained a low ratio of polymerisable groups so that, in the presence of a photo-initiator, they could be cured on demand in situ within 5 minutes under irradiation of blue light to form an intraocular lens within the lens capsule. All resulting polysiloxane soft gels had a low elastic modulus and thus should be able to restore accommodation. The pre-cure viscosity and post-cure modulus of the generated polysiloxanes were controlled by the end group and D4AM concentrations respectively in the re-equilibration reactions. The refractive index could be precisely controlled by adjusting the aromatic ratio in the polymer to suit such application as an artificial lens. Lens stretching experiments with both human and non-human primate cadaver lenses of different ages refilled with polysiloxane polymers provided a significant increase in amplitude of accommodation (up to 4 D more than that of the respective natural lens). Both in vitro cytotoxicity study using L929 cell lines and in vivo biocompatibility study in rabbit models demonstrated the non-cytotoxicity and ocular biocompatibility of the polymer.

show abstract

Structure investigation of organosilicon polymers by silicon-29 NMR

Cited by 78 publications

References 4 publications

A Primer on the Analytical Aspects of Silicones at Trace Levels-Challenges and Artifacts – A Review

A Primer on the Analytical Aspects of Silicones at Trace Levels-Challenges and Artifacts – A Review

A Solid-State NMR Investigation of MQ Silicone Copolymers

High refractive index polysiloxane as Injectable, in situ curable accommodating intraocular lens

Contact Info

Product

Resources

About