BIO-compatibilizers for BLENDing cellulose with synthetic polymers – BIOBLEND

Optimization of a synthetic process requires all products to be structurally characterized using appropriate analytical tools. In order to prepare a new class of molecules such as the targeted compatibilizers, high performance methods have thus to be simultaneously developed in the fields of polymer synthesis and analytical chemistry. This can be successfully achieved providing that a rigorous and step-by-step approach is implemented, starting from small model compounds before considering large polysaccharides, in order to circumvent the two main difficulties associated with the targeted co-polymers: their size and their amphiphilic character. In this context, the BIOBLEND project aims at developing specific methods to synthesize and characterize the copolymeric compatibilizers via an innovative use of existing technologies (controlled radical polymerization, mass spectrometry, nuclear magnetic resonance, transmission electronic microscopy).

Research works performed in the framework of the BIOBLEND project allowed a controlled production of the targeted copolymers. Low solubility of polysaccharide substrates was the main blocking point and led us to prepare these copolymers from cellulose acetate (instead of cellulose-like compounds) prior to subjecting them to a desacetylation step to obtain the initially desired species. Appropriate methodologies have also been developed to evaluate capabilities of so-obtained macromolecules to stabilize cellulose/polystyrene blends.

-

In this multidisciplinary project, scientific advances have been achieved and published in the area of analytical chemistry as well as in the field of polymer chemistry. Main results obtained during this research work were presented in 6 articles in international peer-review journals, 8 international conferences (including 2 invited ones), 2 national conferences, and about 10 posters in both international and national congresses.

The use of natural polymers from renewable resources as an alternative to petroleum-based polymers faces one major issue: the lack of efficient analytical tools required to accurately describe their complex structure. This currently represents a major difficulty in the development of tailored, accurately controlled grafting procedures aimed at modifying natural polymers, such as cellulose, to improve their macroscopic properties. Similar issues are encountered in the alternative strategy consisting of blending natural polymers with synthetic materials of well-established industrial applications. As a result, compatibilizers consisting of cellulose grafted with synthetic chains are developed from cellulose in a semi-empirical manner. To tackle this problematic, we propose a different approach that focuses on the development of both grafting procedures and analytical methodologies on less complex - though relevant – polysaccharides of well-defined smaller size, to produce compatibilizers to be used to stabilize cellulose/polystyrene blends. Overall, the present research project aims at developing analytical methodologies, combining nuclear magnetic resonance and mass spectrometry, to characterize the structure of copolymers consisting of polysaccharidic chains grafted with polystyrene blocks. A systematic analytical control will be performed to assess i) the structure and purity of starting polysaccharides, ii) the coupling yield with reactive group modifiers, iii) the size of the grafted synthetic polymers and iv) the density and uniformity of the grafted blocks. To prepare grafted polystyrene-polysaccharide copolymers, we propose to implement innovative and convenient strategies based on NMP process using the so-called SG1 (phosphorylated N-(2-methylpropyl)-N-(1-diethylphosphono-2,2-dimethyl propyl)-N-oxyl ) as the controlling agent to allow styrene polymerization at quite low temperature, a mandatory condition with regard to the thermal stability of natural polymers. The efficiency of the so-produced copolymers to act as compatibilizers to blend cellulose with PS will be determined, allowing the copolymer synthesis to be optimized in a rational manner and their structure/property relationships to be investigated. Research efforts will be done in both polymerization chemistry and structural spectrometry to design and synthesize these macromolecules, in order to introduce increasing amounts of cellulose into blends with polystyrene. This would inherently increase the final material biodegradability while limiting the use of non-renewable resources.