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CHEM0012 – Polymers Coursework

Format and Rules

All three questions should be answered in prose (continuous sentences). Students are limited to 600 words per question. Words beyond the limit for each question will not be marked.

Submit as doc/docx/odf format only. Do not submit as PDF. You must answer all questions.

Marking is anonymous - PLEASE DO NOT PUT YOUR NAME OR STUDENT NUMBER ANYWHERE ON THE COURSEWORK (including in the file name)

50 marks are available overall.

•    45 marks are available for the three questions (15/20/10, respectively),

•    4 marks available for quality of writing

•    1 mark for providing an AI statement (see below)

Use of AI

This assessment is classified as Section 2- use in an assistive role for AI usage. You can use AI for this coursework, but it is not encouraged. Please note that preliminary testing of these questions using ChatGPT gave incomplete/incorrect answers.

Firstly, you must read UCLs policy on the use of AI here:

https://www.ucl.ac.uk/teaching-learning/generative-ai-hub/three-categories-genai-use-assessment

In your coursework, you must supply an AI statement, beginning with “ I have read and understand the UCL policy on Three categories of GenAI use in assessment.” If you do not understand the policy, please let me  know in advance of the deadline. For the rest of your AI statement:

•    If you don't use AI you must add the statement " AI was not used in the production of this coursework"

•    If you do use AI then you need to give a further 300 word commentary of how you used AI including

o The type of AI used

o How you have amended the AI results

o How you have integrated AI results into your answers

Deadline

Your answers must be submitted by 6th  December 2024 at 17:00 GMT via Moodle Assignment.

Follow-up

A breakdown of your marks will be provided to you as an annotated version of your submission. When scores are released and after all extended submission deadlines have elapsed (likely in the new year), I will upload a document on Moodle in the Polymer section containing  model answers, a summary of common mistakes with corrections, and information on marking for transparency.

Questions

1.    Given a powder of pre-synthesised poly(vinyl acetate), how can you make a bulk solid with high tensile strength? For each step, explain how it will influence mechanical properties. [15]

2.    A sample of isotactic polypropylene is heated above its melting temperature (170 °C) and very slowly

cooled to below its glass transition temperature (-15 °C) down to -50 °C, before being measured by DSC using 3 cycles (named a-c), one after another:

a.    The sample is heated quickly (50 °C min-1) from -40 °C to 250 °C before cooling quickly (50 °C min-1) back to -40 °C

b.   The sample is then heated slowly (1 °C min-1) from -40 °C to 250 °C before cooling slowly (1 °C min-1) back to -40 °C

c.    The sample is finally heated quickly (50 °C min-1) from -40 °C to 700 °C before cooling quickly (50 °C min-1) back to -40 °C

Schematically draw the DSC curves for the three cycles (a-c) each on a separate set of axes. For each, give a brief description of the thermogram features and an explanation of what is happening at a molecular level, comparing to previous cycle(s) where appropriate. [20]

N.B., The graphs maybe created digitally or drawn by hand and scanned. Please ensure the graphs are embedded in the submitted doc/docx/odf file, and not submitted as a separate file.

DSC (Mettler Toledo DSC 3) at UCL

3.    Poly(ethylene glycol) is said to be “more soluble” in water than cellulose acetate. Why is this true (or not), and how might you be able to tell? [10]