Because of its high crystallinity, thermal stability and desirable mechanical properties, but also expressed polarity, nanocellulose was set up as potential reinforcment for polymethacrylate matrices. The purpose of this study was to investigate the influence of nanocellulose (cellulose nanocrystal) fillers on the distribution of molecular weights of the respective matrices, their thermal transitions (glass transition temperatures), thermal stability, surface properties (contact angle) and mechanical properties of prepared nanocomposites. This thesis included ex situ preparation of composites with nanocellulose (1, 2.5 and 5 wt%, 10-20 nm × 300-900 nm with 92% crystallinity) with poly(methyl -methacrylate) (PMMA) and MMA/dimethylaminoethyl methacrylate copolymer (90/10 mol.%) matrices. Amino group in copolymer additionally contributes to the polarity of the matrix. Scanning electron microscope micrographs were used to determine whether nanocellulose forms agglomerates in the polymethacrylate matrix. Prepared composites were characterized by size exclusion chromatography to determine the influence of nanocellulose fillers on the molecular weight and the dispersion of polymer matrices. Differential scanning calorimetry was used to determine the nanocellullse influence on the glass transition temperature. Thermogravimetric analysis was performed to determine the influence of nanocellulose on the thermal stability of the prepared composites. Contact angle measurement with water droplets was performed to assess whether nanocellulose affects the surface wetting. By scanning the surface of the samples by scanning electron microscopy, it was assumed that all the nanocellulose was homogeneously distributed throughout samples. According to the results of differential scanning calorimetry, a trend of increased glass transition temperature with increased mass fraction of cellulose nanocrystals in composites with both matrices could be observed. Size-exclusion chromatography results indicate that hydraulic pressing at elevated temperatures led to a slight degradation of PMMA-prepared composites. For composites prepared with a copolymer, two signals were found; it is assumed that the smaller molecular weight signal belongs to the non-cross-linked molecules and the signal of higher molecular weight to the cross-linked polymer that had formed during hydraulic pressing. The results of thermogravimetric analysis confirm the high thermal stability of the nanocellulose, however, the addition of the nanocellulose filler did not affect thermal decomposition onset temperature of prepared composites. The influence of its mass fraction in the copolymer on the thermal stability of prepared composites is not equivocal; in the case of the PMMA matrix, an increase in the nanocellulose content shifts the degradation curve towards lower temperature values, whereas for the copolymer matrix the opposite is the effect; composites with a higher content of nanocellulose have thermogravimetric curves shifted to higher values. Measurement of the contact angle indicates a decrease in the contact angle with an increased mass fraction of cellulose nanocrystals.