Articles by: Kenneth Hanson

Polymers from Elemental Sulfur

This post is contributed by John Spevacek, an industrial polymer chemist and the author of the blog “It’s the Rheo Thing

While organic chemists are familiar with the elements, very seldom do we ever make use of them as a reactant. Sure, we add elemental magnesium to Grignard reactions and we can add halogens/hydrogen across double bonds, but for the most part, the pure elements are oxidized or reduced or ionized or otherwise modified before they take part in our reactions.

The situation is even that much clearer for my field of polymer chemistry. Pure elements of any sort are just not used at all. We certainly don’t use elemental carbon and hydrogen to make polyolefins, and silicon wafers are useless for making silicone polymers. In short, the refined elements have no place in polymer chemistry.

Until now.

A recent paper in Nature Chemistry (pay-per-view/subscription) showed that elemental sulfur can be directly co-polymerized with an organic molecule. What was more surprising yet was that the polymerization occurred without the use of solvents or even initiators.

From my perspective as a polymer chemist, the uses of sulfur are limited and have historically fallen into three categories. First are the polymers that have the sulfur in the backbone, such as polyphenylene sulfide (PPS), polyethersulfone (PES), and all the countless thiol-ene polymers. Another class are the polymers where the sulfur is peripheral to the backbone, usually as a sulfonate group such as in polystyrene sulfate. And lastly, there are the elastomeric materials where sulfur compounds have been used to vulcanize (crosslink) the polymer chains.

What all three of these sulfur-containing polymers have in common, however, is that none of them are prepared from elemental sulfur. They all require either a reduced or an oxidized form of sulfur in order to form the polymers.

As implied above, this new reaction is very simple. The researchers merely melted the sulfur and added 1,3-diisopropenyl benzene (DIB) at ratios from 90/10 to 50/50 w/w. The S8 rings of sulfur opened up and copolymerized with the vinyl groups.

The reaction mechanism is not explicitly detailed, but I imagine it to be similar to what occurs in thiol-ene polymerizations. Since the organic comonomer is difunctional, the resulting product is crosslinked, not through the sulfur atoms, but instead through the organic monomer. The authors (with tongue-in-cheek) call this “inverse vulcanization”. However, despite the existence of this crosslinking, the polymer still flows as a thermoplastic. (Evidently the numerous sulfide bonds are breaking and reforming under the shear). This is fortunate as it allows the plastic to easily be shaped into a final product using conventional equipment.

While this is the only polymerization reaction I know of using a pure element, this discover by itself is interesting although somewhat limited. Working with molten sulfur imposes two big restraints on the choice of comonomers – that they first be soluble in the molten sulfur and more importantly, that they not volatilize upon exposure to the heat (185 C). In other words, this new reaction opens up only a small set of potential polymers.

But what properties this polymer is already showing!

Consider batteries. We are surrounded in our modern lives by lithium-ion batteries. They are in our cellphones and laptops, our cordless power tools, and even the Mars Curiosity Rover. A relative drawback of these batteries is that the anions are metallic and therefore heavy, reducing the energy density. It’s long been known that lithium-sulfur batteries have a high energy density and lower cost, but the degradation of the sulfur electrodes limits their long-term stability.

Preliminary testing of a lithium battery using this new sulfur-based polymer, however, shows that the performance is nearly identical to that of a standard lithium-sulfur battery but without the degradation. When this result is combined with the ease of processing this new polymer, the potential for lithium-sulfur batteries has suddenly become a lot sunnier.

Almost as sunny yellow as the color of elemental sulfur.

“Get a job, Ken!” Part 2: Proposal Preparation

In my last post I describe the timeline for my faculty job search. In this post, the second in the “Get a job, Ken!” series, I share my strategy for creating and vetting research proposal ideas.

The academic job application consists of a number of items. Most universities ask for a cover letter, CV, letters of recommendation, research proposals, and occasionally other materials (like a teaching statement). A candidate’s appeal to the search committee often depends on the presentation of his/her previous accomplishments (which I’ll discuss in the posts that follow) and, perhaps more importantly, research proposals.

Very few job posts provide guidelines for proposals. My understanding is that search committees want to see two or three original research ideas that are:

  1. Different from the work of previous advisors.
  2. Unique enough to show creativity and the ability to compete with others in the field.
  3. Interesting enough to be potentially fundable.

Many people, me included, encourage those planning to apply for faculty positions to start thinking about original research ideas while in graduate school. Thinking about proposals early allows time to work through ideas as well as build a broad knowledge based about cutting-edge research. Not everyone will come up with a new, creative idea while in graduate school, but it’s helpful to start practicing and developing the strategies to do so early.

One strategy to fuel the creative process includes learning about research outside of your immediate field. While reading papers or walking though poster sessions, ask yourself: “How could this research contribute to my work?” and “How could my expertise contribute to their work?” Many major research advances bridge the gap between sub-disciplines. Gap-bridging ideas also have greater potential to appeal to more members of the search committee. Most academic hires are decided by entire departments, representing individuals from all ‘flavors’ of chemistry.

Quick aside: be cautious when getting excited about a new idea. It is very disappointing to come up with a ‘new idea’ and then discover after a literature search that someone else has already published it. Yet, this unfortunate event has a silver lining. It suggests you’re on the right track to coming up with feasible/publishable ideas.

Coming up with new ideas is difficult. There is also a large activation barrier to formalizing new ideas and writing them as a research proposal. There are many strategies to start and maintain the process, such as establishing incentives, deadlines, punishments, etc. In contrast to these self- dependent and willpower-driven strategies, I found joining/creating an Aspiring Professors Support Group especially helpful.

Our Aspiring Professor Support Group was composed of individuals interested in applying for academic jobs (either in 2012 or beyond) in various domains of chemistry, including organic, inorganic, analytical, and physical.  The members of the support group respected and trusted each other – an important factor. We were comfortable sharing our ideas and there were no concerns about anyone stealing and misrepresenting other’s ideas as their own. Once the support group was formed, we set up meetings—with deadlines—for presenting our research ideas.

We began meeting once a week in early July, 2012. At each meeting three people gave either a chalk talk or power point presentation on one proposal idea (6 people x 3 proposals each = 18 proposals over 6 weeks). Scheduling the presentations gave us a tangible deadline and forced us to think through and prepare our proposals before job applications were due.

These meetings served as the first filter, outside of our own minds, to gauge whether we should commit to writing down a particular proposal. We presented and defended our ideas in front of an audience and if there were fundamental flaws with a proposal—like infeasibility or impossibility—they were abandoned or revamped. The diversity of our Aspiring Professors Support Group also proved an important opportunity to see how chemists from other areas/domains responded to each idea. The group’s questions helped prepare me for the questions I might be asked during an actual interview.

In addition to formalizing ideas, the group was also helpful in other aspects of the job search. We sent new job openings to each other and shared anecdotes/stories/advice for the application process.

In the next blog post I’ll describe the next step: putting research proposals on paper.

By April 29, 2013 3 comments Uncategorized

“Get a job, Ken!” Part 1: The Timeline

The application process for chemistry faculty positions can last several (grueling) months. The timeline below is my 2012 job search and serves as the first installment of my “Get a Job, Ken!” blog post series.

Job postings: The postings for inorganic/energy/materials assistant professor positions at top 100, R1 institutions (in the United States) began appearing in July 2012 and continued until about November. Postings for professor positions at undergraduate-focused institutions continued well beyond into Spring 2013.

Application deadlines: The distribution of deadlines for the 38 positions I applied to are shown in the bar graph below. The first deadline was on September 10th. The last was on December 1st. The most popular due date by far was October 15th.

Interviews: I’ve heard of people receiving phone calls offering interviews as early as two weeks after the application deadline. Other people recounted receiving calls as late as February/March after search committees failed to find a viable candidate during their first round of interviews.

Rejection letters/emails: Some universities send rejection emails/letters after selecting candidates to interview (as early as November) while others send emails after making an offer to their top candidate. Some universities don’t send anything at all (10-20% of the schools I applied to).

Decisions, second visits and negotiations: Job offers are usually proffered between December and March. Second visits—a department’s chance to entice their top candidate to accept the offer—are scheduled soon after. Negotiations about start-up funds, lab space, teaching assignments and so on occur during the month following the offer and will continue until the final contract is signed (or rejected).

Graduate student recruiting weekend: If newly hired professors receive and accept an offer in time, they can potentially attend their new institution’s graduate student recruiting weekend. This event provides a chance for new professors to meet and start recruiting students to help establish their research group.

Start date: The most common start dates I saw listed on the job postings were July 1st or August 1st, but the actual start date is negotiable (to some degree).

As a real-life example, here is the start-to-finish timeline for the search process that ultimately ended in my assistant professor position at FSU:

  • Application deadline: December 1st
  • Request for phone interview: January 9th
  • Phone interview: January 16th
  • Request for in-person interview: January 23rd
  • In-person interview: February 10-13th
  • Offer: February 20th
  • Second visit: March 8-11th
  • Negotiation: February 20th to March 22nd
  • Formal Acceptance: March 27th
  • Graduate student recruiting weekend: March 29th
  • Official start date: August 8th 

By April 23, 2013 1 comment Uncategorized

“Get a job, Ken!”

It has been several months since my last post, but I have (what I think is) a reasonable excuse: I’ve been trying to get a job. The demanding mantra endlessly looping in my brain for the last six months was, “Get a job, Ken!” Applying for chemistry faculty positions at R1 institutions has been a trial both scientifically and emotionally, especially since the likelihood of landing such a job is increasingly the exception rather than the norm. I’ve very glad my search is over and I humbly and yet happily share that I will be starting as an assistant professor at Florida State University in the fall (August 2013).

Reflecting on the job search, I found that there were very few resources that helped me understand what to expect beforehand. This is probably especially true for someone like me who did not come from institutions more traditionally known for producing professors, like Cal Tech, MIT, and Berkeley. I did not spend my undergraduate and graduate years observing and learning from older coworkers/friends going through the faculty job search process before me. To my surprise, I also found little online about the chemistry faculty job search and what makes it different from other job searches. Instead, I spent a lot of time gleaning hints and tips from coworkers, advisors, professors and anyone that would answer my questions. Hoping to help those entering the search after me, while also building on previous blog posts where I share advice for new graduate students and post-doc position seekers, my next series of blog posts will outline my faculty job search experience.

Most of the advice I’ll share is based on my own anecdotal experiences or the stories I’ve heard from others. These experiences vary widely and, when preparing for your own job search, I encourage job seekers to consult with as many people as possible and load-up on advice. I also hope others will share more in the comment section.

Another thing to note is that my experience was specifically with faculty positions relating to materials, inorganic, and any energy related research. Yet, even with this emphasis, it’s possible that many of the suggestions are still applicable to primarily undergrad or even an industry job-seeker.

Since I find myself with so much to share (as well as hesitant to ask readers to read a mega-post all at once) I am going to partition the “Get a Job, Ken!” experience into the following posts covering eight different aspects of the job application process:

  1. The Timeline
  2. Proposal Preparation
  3. Proposal Format
  4. Other Content
  5. Submitting and Waiting
  6. Phone and On-site Interviews
  7. Research/Proposal Talks and Meeting with the Chair
  8. The Offer, Second Visit, and Negotiation

I hope you find them useful.

By April 20, 2013 7 comments Uncategorized