Catalyst breaks sulfur–sulfur bonds to give new life to tired tyres

An image showing car tyres

Process recovers organic components that can become new elastomers

Researchers from Canada have demonstrated a mild chemical approach for reclaiming organic polymers from waste tyre rubber. Their Lewis acid-catalysed reductive silylation process could reduce the environmental impact of used sulfur-crosslinked elastomers.

‘The recovery of vulcanised rubbers is a major environmental problem, whose solution is still open,’ comments Carlos Scuracchio, who works on rubber recycling at the Federal University of São Carlos, Brazil. The high stability of vulcanised tyre rubber makes it challenging to recycle; toxic constituents may leach into the environment from used tyre stockpiles and fires at such locations can be dangerous, very polluting and difficult to arrest. 

Michael Brook from McMaster University, who led the team behind the new silylation process has first-hand experience of tyre fires. ‘About 15 years or 20 years ago, not far from where I live in Hamilton, there was a really bad tyre fire. The byproducts of that were not good news for the local environment.’ 

Now, Brook’s team has shown that hydrosilanes, catalysed by B(C6F5)3, can effectively reduce sulfur–sulfur bonds in complex sulfur-crosslinked tyre rubbers in yields of up to 90%. They demonstrated their process on bicycle inner tubes, solid tyres and tyre crumb, and the resulting polymeric, silyl-protected thiolated oils were straightforward to separate by filtration or centrifugation. The team also showed they could radically or oxidatively crosslink the resulting oils to generate new elastomers, from which they created a new toy tyre as a proof of concept.

A scheme showing how the reductive silylation of RS-SR bonds to silyl thio ethers using a variety of hydrosilicones occurs in the presence of B(C6F5)3
Source: © Michael Brook/McMaster University
Reductive silylation of RS–SR bonds to silyl thio ethers using a variety of hydrosilicones in the presence of B(C6F5)3 could be developed into a recycling process for car tyres

‘We were surprised that you could actually get the rubber to dissolve and be converted back to liquid polymeric materials. I didn’t expect it to happen quite as well as it did,’ explains Brook. He says there is ‘really very little out there in the literature’ on the depolymerisation of sulfur-cured rubbers, and that ‘if there were a commercially viable process, people would be using it’. However, with 10wt% of ‘quite expensive’ catalyst being required to reduce the used tyre rubber, Brook clarifies that ‘there’s no way in my view that today this is a commercial process. But I think it opens the door into thinking about different ways to degrade the rubbers to make useful polymers again.’ The team are already optimising the process to reduce the quantity of catalyst it requires.

‘Most rubber recycling techniques generate materials that are difficult to mould and process and have quite different properties from the original raw materials,’ adds Scuracchio. ‘At this point, a very interesting part of the work is that the rubber can be processed without worrying about possible contamination, and the material produced is a rheologically simple oil capable of being moulded and transformed back into a solid product. This factor makes the method very promising in the field of rubber recycling.’

References: This article is open access S Zheng et al, Green Chem., 2019, DOI: 10.1039/c9gc03545a

Royal Society of Chemistry - ChemistryWorld
BY RUTH ZADIK 17 DECEMBER 2019

 

Teaching-Track Assistant Professor

Department of Chemistry & Chemical Biology, McMaster University 

The Department of Chemistry & Chemical Biology invites applications for a teaching-track faculty position at the Assistant Professor level, effective July 1, 2020. Applicants must hold a Ph.D. in Chemistry at the time of appointment and should have a demonstrated record of teaching excellence at the undergraduate level. The duties will involve teaching a range of courses, including general (first-year) chemistry and higher level courses in Chemistry and/or Chemical Biology, as well as administrative service. Participation in curriculum development and/or undergraduate laboratory supervision may also be required. There is no expectation that the candidate will develop an independent research program or engage in collaborative research in the chemical sciences, but pedagogic research relevant to chemistry would be encouraged.  

McMaster University is a globally renowned institution of higher learning and a research community committed to advancing human and societal health and well-being. Our focus on collaboratively exchanging ideas and approaches makes us uniquely positioned to pioneer ground-breaking solutions to real-world problems leading to a Brighter World. The Faculty of Science works to create global impact by advancing scientific discovery and knowledge, and promoting greater understanding. Our innovative, interdisciplinary approach generates new methods and insights, results, and lasting change. 

McMaster University has a strong commitment to achieving diversity among faculty and staff that reflects the multicultural makeup of our student body. The successful candidate will be committed to inclusion and excellence. The search Committee is especially interested in candidates who can contribute, through their teaching and/or service, to the diversity of the academic community. Women and applicants from traditionally underrepresented populations are strongly encouraged to apply. Gender diversity is being addressed at McMaster University through our policies and actions. Recent actions in this area include the completion of a gender pay equity study and a resultant base salary adjustment applied to all female faculty members in July 2015, as well as a recent commitment by McMaster to the nation-wide Dimensions EDI charter (http://www.nserc-crsng.gc.ca/NSERC-CRSNG/EDI-EDI/Dimensions_Dimensions_eng.asp).

Faculty members at McMaster University enjoy a number of personal and professional benefits. University employees are offered an excellent benefits package that includes, but is not limited to, extended health care benefits, dental care, group life, long term disability, worldwide travel assistance, and a retirement plan. Progressive policies are in place to assist faculty members who become parents or are needed to care for family members. Salary will be commensurate with qualifications and experience.  

Applications must include a cover letter, curriculum vitae, a teaching dossier that includes a statement of teaching philosophy and evidence of teaching experience and effectiveness, and a one-page statement on equity and diversity. Applicants should also arrange to have three referees provide a confidential letter of reference, sent by e-mail to the Chair (chair@chemistry.mcmaster.ca). Reference letters should include the candidate’s name in the file name (Last_First.pdf) and should be submitted as a PDF, on letterhead, and from an email address that is associated with the institution or organization of origin. Complete applications must be made online at hr.mcmaster.ca/careers (Faculty Positions, Job ID 29497) to the attention of:
Dr. Gillian Goward, Professor & Chair
Department of Chemistry & Chemical Biology
McMaster University
1280 Main Street West
Hamilton, Ontario, Canada, L8S 4K1 

Review of complete applications will begin February 1, 2020, and continue until the position is filled. The effective date of appointment is expected to be on July 1, 2020. All applicants will receive an on-line confirmation of receipt of their application; however, only short-listed applicants will be contacted for interviews. 

All qualified candidates are encouraged to apply; however, Canadian citizens and permanent residents will be given priority. To comply with the Government of Canada’s reporting requirements, the University is obliged to gather information about applicants’ status as either Permanent Residents of Canada or Canadian citizens. Applicants need not identify their country of origin or current citizenship; however, all applications must include one of the following statements:
Yes, I am a citizen or permanent resident of Canada
No, I am not a citizen or permanent resident of Canada. 

McMaster University is located on the traditional territories of the Haudenosaunee and Mississauga Nations and, within the lands protected by the “Dish With One Spoon” wampum agreement. In keeping with its Statement on Building an Inclusive Community with a Shared Purpose, McMaster University strives to embody the values of respect, collaboration and diversity, and has a strong commitment to employment equity. The diversity of our workforce is at the core of our innovation and creativity and strengthens our research and teaching excellence. The University seeks qualified candidates who share our commitment to equity, diversity and inclusion. While all qualified candidates are invited to apply, we particularly welcome applications from women, persons with disabilities, First Nations, Métis and Inuit peoples, members of visible minorities, and LGBTQ+ persons.  

Job applicants requiring accommodation to participate in the hiring process should contact the Human Resources Service Centre at 905-525-9140 ext. 222-HR (22247) to communicate accommodation needs. 

Dr. Britz McKibbin, a Diet Detective

Diet detectives


Researchers at McMaster have identified several chemical signatures, detectable in blood and urine, that can accurately measure dietary intake, potentially offering a new tool for physicians, dietitians and researchers to assess eating habits, measure the value of fad diets and develop health policies.

The research, published in the journal Nutrients, addresses a major challenge in assessing diets: studies in nutrition largely rely on participants to record their own food intake, which is subject to human error, forgetfulness or omission.

“This has been a major issue in nutritional research and may be one of the main reasons for the lack of real progress in nutritional sciences and chronic disease prevention,” says Philip Britz-McKibbin, a professor in the Department of Chemistry and Chemical Biology at McMaster University and lead author of the study, which was a collaboration with Dr. Sonia Anand and colleagues from the Departments of Medicine, and Health Research, Evidence, and Impact.

Scientists set out to determine if they could identify chemical signatures, or metabolites, that reflect changes in dietary intake, measure those markers and then compare the data with the foods study participants were provided and then reported they had eaten. The specimens analyzed were from healthy individuals who participated in the Diet and Gene Intervention Study (DIGEST).

Over a two-week period, researchers studied two contrasting diets: the Prudent diet,  rich in fruits, vegetables, lean meats, and whole grains, and a contemporary Western diet, rich in trans fats, processed foods, red meat and sweetened beverages.

Researchers were able to validate a panel of metabolites in urine and plasma that correlated with the participants’ consumption of fruits, vegetables, protein and/or fiber.

“We were able to detect short-term changes in dietary patterns which could be  measured objectively,” says Britz-McKibbin. “And it didn’t take long for these significant changes to become apparent.”

Britz-McKibbin cautions that food chemistry is highly complex. Our diets are composed of thousands of different kinds of chemicals, he says, and researchers don’t know what role they all may play in overall health.

In future, he hopes to broaden this work by examining a larger cohort of participants over a longer period of time. His team is also exploring several ways to assess maternal nutrition during crucial stages of fetal development and its impact on obesity and metabolic syndrome risk in children.

The study was funded by the Natural Sciences and Engineering Research Council of Canada, Genome Canada, Labarge Optimal Aging Initiative Opportunities Fund, and the Faculty of Science at McMaster.

Photo by Flickr Creative Commons/Allen Sheffield


BY MICHELLE DONOVAN

OCTOBER 24, 2019

Tenure-Track Assistant Professor in Environmental Chemistry Department of Chemistry & Chemical Biology, McMaster University

The Department of Chemistry & Chemical Biology (CCB) at McMaster University invites applications to fill a tenure-track position at the rank of Assistant Professor in the area of Environmental Chemistry, effective July 1, 2020. Scientists whose research interests focus on developing and implementing state-of-the-art analytical chemistry methods for the analysis of chemical contaminants and environmental toxins relevant to human health are encouraged to apply. The successful applicant will be expected to mount an innovative and multidisciplinary research program under the umbrella of environmental chemistry broadly defined, which may touch on aspects such as the analysis of chemical exposures, land, air and water remediation, and the study of chemical breakdown pathways under changing climate conditions. The research program should contribute to fundamental discoveries in emerging areas of environmental chemistry, such as environmental toxicology and exposure biology (i.e. exposomics). The central role of chemistry in understanding and resolving environmental issues is a clear area of growing importance, and CCB will provide a vibrant environment to foster a translational research program in this area, with opportunities for both internal and external collaborations, including the United Nations University – Institute for Water, Environmental and Health that is located at McMaster University.  

Our aim is to recruit a candidate who will establish an internationally competitive research program and forge numerous research interactions and collaborations with colleagues in the Faculty of Science, and other Faculties, including Engineering. Integration between Faculty of Science & Faculty of Engineering will be a key objective of this new position. The successful candidate will take advantage of numerous opportunities to attract research funding for personnel and infrastructure, including a variety of grant programs from the Natural Science and Engineering Research Council of Canada (NSERC), as well as collaborative interactions with governmental agencies and the private sector.  

The research program of the selected candidate will be located in a newly-renovated laboratory space, which was constructed in the Spring of 2019, and is shared with Engineering faculty. This space includes state-of-the-art open-concept laboratories designed for all aspects of synthetic, analytical, and physical chemistry. The candidate will benefit from the surrounding suites of shared infrastructure (Optical Spectrometers, Raman spectrometers, Device Fabrication facilities, etc.). In addition to having access to the equipment and facilities in this new space, the successful candidate will also have access to instrumentation in the CCB Core Facilities (Magnetic Resonance, Mass Spectrometry, and X-ray Diffraction), the Canadian Centre for Electron Microscopy, the Biointerfaces Institute, and the Centre for Emerging Device Technologies (CEDT).  

Applicants should clearly demonstrate potential to develop a prominent, externally funded research program and a commitment to excellence in teaching at the graduate and undergraduate levels. Candidates must have a bachelor’s and doctoral degree in chemistry, chemical biology, or a closely related chemistry-based field, relevant postdoctoral experience, and a promising record of research scholarship and productivity. A complete application package must include a cover letter, a detailed curriculum vitae, a one-page statement of teaching philosophy, and detailed descriptions of at least three research projects that exemplify the proposed research program. In addition, applicants are asked to provide a one-page description of their commitment to and demonstrated experience of advancing equity, diversity and inclusion in post-secondary education, community-based or other professional settings. Applicants should also include a one-to-two page summary highlighting their top three publications and specifying the signficance and novelty of these contributions, as well as a list of the major instrumentation and equipment necessary to pursue the proposed research program. A minimum of three academic reference letters should be sent via e-mail directly from referees to chair@chemistry.mcmaster.ca. Reference letters should include the candidate’s name in the file name (Last_First.pdf) and should be submitted as a PDF, on letterhead, and from an email address that is associated with the institution or organization of origin.  

McMaster University is a globally renowned institution of higher learning and a research community committed to advancing human and societal health and well-being. Our focus on collaboratively exchanging ideas and approaches makes us uniquely positioned to pioneer groundbreaking solutions to real-world problems leading to a Brighter World. The Faculty of Science works to create global impact by advancing scientific discovery and knowledge, and promoting greater understanding. Our innovative, interdisciplinary approach generates new methods and insights, results, and lasting change. 

McMaster University has a strong commitment to achieving diversity among faculty and staff that reflects the diversity of our student body. The successful candidate will be committed to inclusion and excellence and the Department is especially interested in candidates who can contribute, through their teaching and/or service, to the diversity of the academic community. Women, persons with disabilities, First Nations, Metis and Inuit persons, members of racialized communities and LGBTQ-identified persons are strongly encouraged to apply. Gender diversity is being addressed at McMaster University through our policies and actions. Recent actions in this area include the completion of a gender pay equity study and a resultant base salary adjustment applied to all female faculty members in July 2015, as well as a recent commitment by McMaster to the nation-wide Dimensions EDI charter (http://www.nserc-crsng.gc.ca/NSERC-CRSNG/EDI-EDI/Dimensions_Dimensions_eng.asp). 

Faculty members at McMaster University enjoy numerous personal and professional benefits. University employees are offered an excellent benefits package that includes, but is not limited to, extended health care benefits, dental care, group life insurance, long term disability, worldwide travel assistance, and a retirement plan. Progressive policies are in place to assist faculty members who become parents or are needed to care for family members. Salary will be commensurate with qualifications and experience. 

Complete applications must be made online at hr.mcmaster.ca/careers (Faculty Positions, Job ID 28623) to the attention of:
Dr. Alex Adronov, Professor & Acting Chair
Department of Chemistry & Chemical Biology
McMaster University
1280 Main Street West
Hamilton, Ontario, Canada, L8S 4K1 

Review of complete applications will begin December 1,2019, and continue until the position is filled. The effective date of appointment is expected to be July 1st, 2020. All applicants will receive an on-line confirmation of receipt of their application; however, only short-listed applicants will be contacted for interviews. 

All qualified candidates are encouraged to apply; however, Canadian citizens and permanent residents will be given priority. To comply with the Government of Canada’s reporting requirements, the University is obliged to gather information about applicants’ status as either Permanent Residents of Canada or Canadian citizens. Applicants need not identify their country of origin or current citizenship; however, all applications must include one of the following statements:  

Yes, I am a citizen or permanent resident of Canada
No, I am not a citizen or permanent resident of Canada.

McMaster University is located on the traditional territories of the Haudenosaunee and Mississauga Nations and, within the lands protected by the “Dish With One Spoon” wampum agreement. In keeping with its Statement on Building an Inclusive Community with a Shared Purpose, McMaster University strives to embody the values of respect, collaboration and diversity, and has a strong commitment to employment equity. The diversity of our workforce is at the core of our innovation and creativity and strengthens our research and teaching excellence. The University seeks qualified candidates who share our commitment to equity, diversity and inclusion. While all qualified candidates are invited to apply, we particularly welcome applications from women, persons with disabilities, First Nations, Métis and Inuit peoples, members of visible minorities, and LGBTQ+ persons.  

Job applicants requiring accommodation to participate in the hiring process should contact the Human Resources Service Centre at 905-525-9140 ext. 222-HR (22247) o to communicate accommodation needs. 
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McMaster University - Faculty of Science | Chemistry & Chemical Biology