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Department of Chemistry & Chemical Biology













Department of Chemistry & Chemical Biology – Ph.D. Departmental Seminar – Sijia Zheng
	
 May 7, 2020 
 1:30PM to 2:30PM





Event Categories  Grad Events and  Seminars






























Date/Time

Date(s) - 07/05/2020
1:30 pm - 2:30 pm





TITLE:                        New Routes to Functional Silicone Elastomers through Sulfur Chemistry 


DATE:                         Thursday, May 7, 2020 


TIME:                          1:30 p.m.  


ZOOM:                   contact macchem@mcmaster.ca for Zoom link and password


SUPERVISOR:  Dr. Mike Brook 


ABSTRACT: 


Siliconeselastomers are widely used for their unique properties when compared tocarbon-based counterparts. Synthetic methods for their synthesis are stillquite limited. Traditional silicone products are no longer able to meet therequirement for modern materials. I have therefore developed siliconeelastomers with customized structures and improved sustainability that will beable to facilitate the development of next generation materials.


Sulfurand its functional groups is a growing player in modern polymer and materialsscience, since sulfur reactions are exceptionally versatile and useful. Theincorporation of sulfur reactions into silicone precursors leads to siliconematerials with unique properties for various research interests.


Inthis presentation, we first demonstrate general and simple method for 3Dprinting silicone elastomers using photoinitiated thiol-ene chemistry. Unlikeother radical processes, the relatively oxygen insensitive thiol-ene provideboth a rapid reaction rate and rapid necessary build up of the viscosity (<2seconds) in the presence of air. A variety of customized silicone structures,containing more than one modulus, can be obtained with relatively fast printingspeed. 


Thepresentation will also summarize our research on the development of redoxreversible silicone elastomers based on disulfide linkages. Disulfide-linkedelastomeric silicone materials were prepared by oxidizing thiopropylsiliconeoil with oxidants (PhI(OAc)2 orNaClO). Reductive cleavage of the disulfide bridge was successfully performedwith the hydrosilanes and B(C6F5)3 catalyst.


Thisestablished method for disulfide reductive cleavage was extended to thedisulfides and polysulfide linkages found in used rubber materials. Variouskinds of sulfur-cured rubbers were successfully devulcanized to polymeric oils.This simple and efficient method could potentially offer a solution to theproblem of the huge amounts of tire waste produced every year.